diff --git a/src/tools/handlers.rs b/src/tools/handlers.rs
index 5176959..9c3e9e7 100644
--- a/src/tools/handlers.rs
+++ b/src/tools/handlers.rs
@@ -9,6 +9,15 @@
 //! condition, which is what a caller with the input in front of them needs;
 //! the handler adds the parameter name so that the form can highlight the
 //! field.
+//!
+//! 工具处理函数。
+//!
+//! 每个处理函数接收已校验的参数，并调用 `apsis-rs` 的公共接口。结果由
+//! [`super::out`] 塑造，使前端对所有工具都用同一批组件渲染。
+//!
+//! 错误通过 [`ToolError`] 报告，消息为表单的使用者而写。`apsis-rs` 底层的错误
+//! 类型描述了具体状况，那正是手头有输入的调用方所需要的；处理函数补上参数名，
+//! 使表单能够高亮该字段。
 
 use apsis::apsis_coord::{Ecef, Eci, Geodetic};
 use apsis::apsis_frames::EarthRotationAngle;
@@ -27,6 +36,10 @@ use crate::tools::{Params, ToolError};
 ///
 /// The identifier is one of the identifiers in the registry; an unknown one
 /// is reported as a general failure.
+///
+/// 按标识运行一个工具。
+///
+/// 标识是注册表中的标识之一；未知的标识被报告为一般性失败。
 pub fn run(id: &str, params: &Params<'_>) -> Result<Value, ToolError> {
     match id {
         "parse-tle" => parse_tle(params),
@@ -43,6 +56,7 @@ pub fn run(id: &str, params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Parses a two-line element set and reports its fields.
+/// 解析两行元素集并报告其各字段。
 fn parse_tle(params: &Params<'_>) -> Result<Value, ToolError> {
     let text = params.text("tle")?;
     let element = TwoLineElement::parse(&text).map_err(|error| {
@@ -156,6 +170,7 @@ fn parse_tle(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Propagates one instant with SGP4 and reports the state.
+/// 用 SGP4 传播某一时刻并报告状态。
 fn sgp4_propagate(params: &Params<'_>) -> Result<Value, ToolError> {
     let text = params.text("tle")?;
     let model = gravity_model(params.choice("model")?);
@@ -245,6 +260,7 @@ fn sgp4_propagate(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Samples a ground track and returns the points.
+/// 对地面轨迹采样并返回各点。
 fn sgp4_track(params: &Params<'_>) -> Result<Value, ToolError> {
     let text = params.text("tle")?;
     let model = gravity_model(params.choice("model")?);
@@ -341,6 +357,8 @@ fn sgp4_track(params: &Params<'_>) -> Result<Value, ToolError> {
     .map(|value| {
         // The time axis is carried separately so that the chart can label
         // the abscissa without reading the table.
+
+        // 时间轴单独携带，使图表无需读取表格即可标注横坐标。
         let mut members = value.members().to_vec();
         members.push((
             "axis".to_string(),
@@ -355,6 +373,7 @@ fn sgp4_track(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Compares the mean elements with the osculating elements.
+/// 把平均根数与密切根数作比较。
 fn orbit_osculating(params: &Params<'_>) -> Result<Value, ToolError> {
     let text = params.text("tle")?;
     let model = gravity_model(params.choice("model")?);
@@ -480,6 +499,7 @@ fn orbit_osculating(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Converts Keplerian elements to a state vector.
+/// 把开普勒根数转换为状态矢量。
 fn kepler_state(params: &Params<'_>) -> Result<Value, ToolError> {
     let parameter = gravity_parameter(params.choice("model")?);
     let elements = KeplerianElements {
@@ -594,6 +614,7 @@ fn kepler_state(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Converts an instant between time scales.
+/// 在时间尺度之间转换一个时刻。
 fn time_convert(params: &Params<'_>) -> Result<Value, ToolError> {
     let scale = time_scale(params.choice("scale")?);
     let form = params.choice("input")?;
@@ -647,6 +668,9 @@ fn time_convert(params: &Params<'_>) -> Result<Value, ToolError> {
             if let Some(mjd) = mjd {
                 // The label names the scale the input was given on, so it
                 // is built rather than looked up.
+
+                // 标签要指出输入所用的尺度，因此它是构造出来的，而不是查表得到
+                // 的。
                 scalars.push(Scalar::with_unit(
                     format!("Input on {}", target.name()),
                     out::fmt(mjd, 9),
@@ -700,6 +724,7 @@ fn time_convert(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Converts a geodetic position to Earth-fixed coordinates.
+/// 把大地位置转换为地固坐标。
 fn geodetic_ecef(params: &Params<'_>) -> Result<Value, ToolError> {
     let latitude = out::radians(params.number("latitude")?);
     let longitude = out::radians(params.number("longitude")?);
@@ -780,6 +805,7 @@ fn geodetic_ecef(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Rotates a vector between the inertial and Earth-fixed frames.
+/// 在惯性系与地固系之间旋转一个矢量。
 fn frame_transform(params: &Params<'_>) -> Result<Value, ToolError> {
     let direction = params.choice("direction")?;
     let vector = apsis::apsis_math::Vec3::new(
@@ -864,6 +890,11 @@ fn frame_transform(params: &Params<'_>) -> Result<Value, ToolError> {
 /// whose perigee touches the lower orbit and whose apogee touches the upper
 /// one, a coast for half the ellipse's period, and a second burn onto the
 /// destination circle.
+///
+/// 规划两个圆轨道之间的霍曼转移。
+///
+/// 该转移是经典的两脉冲机动：一次点火进入一个近地点触及低轨、远地点触及高轨的
+/// 椭圆，滑行半个椭圆周期，再一次点火进入目标圆轨道。
 fn hohmann_transfer(params: &Params<'_>) -> Result<Value, ToolError> {
     let from_radius = params.number("from_radius")?;
     let to_radius = params.number("to_radius")?;
@@ -966,6 +997,7 @@ fn hohmann_transfer(params: &Params<'_>) -> Result<Value, ToolError> {
 }
 
 /// Returns the gravity model named by a select value.
+/// 返回某个选择值所命名的重力模型。
 fn gravity_model(value: &str) -> GravityModel {
     match value {
         "wgs84" => GravityModel::WGS84,
@@ -974,6 +1006,7 @@ fn gravity_model(value: &str) -> GravityModel {
 }
 
 /// Returns the display name of a gravity model select value.
+/// 返回某个重力模型选择值的显示名。
 fn gravity_model_name(value: &str) -> &'static str {
     match value {
         "wgs84" => "WGS 84",
@@ -982,6 +1015,7 @@ fn gravity_model_name(value: &str) -> &'static str {
 }
 
 /// Returns the Chinese display name of a gravity model select value.
+/// 返回某个重力模型选择值的中文显示名。
 fn gravity_model_name_zh(value: &str) -> &'static str {
     match value {
         "wgs84" => "WGS 84",
@@ -990,6 +1024,7 @@ fn gravity_model_name_zh(value: &str) -> &'static str {
 }
 
 /// Returns the gravitational parameter of a gravity model select value.
+/// 返回某个重力模型选择值的引力参数。
 fn gravity_parameter(value: &str) -> GravityParameter {
     match value {
         "wgs84" => GravityParameter::WGS84,
@@ -998,6 +1033,7 @@ fn gravity_parameter(value: &str) -> GravityParameter {
 }
 
 /// Returns the time scale named by a select value.
+/// 返回某个选择值所命名的时间尺度。
 fn time_scale(value: &str) -> TimeScale {
     match value {
         "tai" => TimeScale::Tai,
@@ -1008,6 +1044,7 @@ fn time_scale(value: &str) -> TimeScale {
 }
 
 /// Formats an epoch as a UTC calendar string.
+/// 把历元格式化为 UTC 日历字符串。
 fn format_calendar(epoch: Epoch) -> String {
     match epoch.calendar(TimeScale::Utc) {
         Some(calendar) => format_calendar_text(calendar),
@@ -1016,6 +1053,7 @@ fn format_calendar(epoch: Epoch) -> String {
 }
 
 /// Formats a calendar value.
+/// 格式化一个日历值。
 fn format_calendar_text(calendar: Calendar) -> String {
     format!(
         "{:04}-{:02}-{:02}T{:02}:{:02}:{:09.6}",
@@ -1032,6 +1070,10 @@ fn format_calendar_text(calendar: Calendar) -> String {
 ///
 /// An empty slice returns not-a-number for both, which encodes as `null` and
 /// is rendered by the frontend as a missing value.
+///
+/// 返回切片中的最小值与最大值。
+///
+/// 空切片对两者都返回非数，它编码为 `null`，并由前端渲染为缺失值。
 fn min_max(values: &[f64]) -> (f64, f64) {
     let mut minimum = f64::NAN;
     let mut maximum = f64::NAN;
@@ -1054,6 +1096,11 @@ fn min_max(values: &[f64]) -> (f64, f64) {
 ///
 /// The estimate uses Kepler's third law with the WGS 72 gravitational
 /// parameter, so it is the size of the circular orbit with that mean motion.
+///
+/// 估计某个平均运动所隐含的半长轴。
+///
+/// 该估计使用开普勒第三定律与 WGS 72 引力参数，因此它是具有该平均运动的圆轨道
+/// 的大小。
 fn semi_major_axis_estimate(mean_motion: f64) -> f64 {
     if mean_motion <= 0.0 {
         return f64::NAN;
diff --git a/tests/api.rs b/tests/api.rs
index 3a67cb6..a475cdd 100644
--- a/tests/api.rs
+++ b/tests/api.rs
@@ -1,9 +1,15 @@
 //! Tests for the router and the payloads it encodes.
+//! 路由器及其编码的载荷的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use std::sync::Arc;
 
 use apsis_book::api::*;
@@ -25,6 +31,9 @@ fn router() -> Router {
 fn get(router: &Router, path: &str) -> Response {
     // The request parser splits the target, so a test that wants a query
     // supplies it in the path and it is split the same way here.
+
+    // 请求解析器会拆分目标，因此想要查询的测试把它写在路径里，这里也以同样的
+    // 方式拆分。
     let (path, query) = match path.split_once('?') {
         Some((path, query)) => (path.to_string(), Some(query.to_string())),
         None => (path.to_string(), None),
@@ -212,6 +221,8 @@ fn malformed_bodies_are_rejected() {
 fn a_hashed_asset_is_immutable_and_a_plain_one_is_not() {
     // A content hash in the name means the name changes with the
     // contents, so the browser can keep it for as long as it likes.
+
+    // 名字中含内容哈希意味着名字随内容变化，因此浏览器可以想存多久就存多久。
     assert_eq!(
         cache_policy("assets/index-Vou83oaV.js"),
         "public, max-age=31536000, immutable"
@@ -221,10 +232,12 @@ fn a_hashed_asset_is_immutable_and_a_plain_one_is_not() {
         "public, max-age=31536000, immutable"
     );
     // A name without one is reused by the next build.
+    // 不含哈希的名字会被下一次构建复用。
     assert_eq!(cache_policy("index.html"), UNHASHED_CACHE_POLICY);
     assert_eq!(cache_policy("assets/app.js"), UNHASHED_CACHE_POLICY);
     assert_eq!(cache_policy("favicon.ico"), UNHASHED_CACHE_POLICY);
     // A name that merely ends in a dash is not hashed.
+    // 仅仅以连字符结尾的名字不算带哈希。
     assert_eq!(cache_policy("assets/app-.js"), UNHASHED_CACHE_POLICY);
     assert_eq!(cache_policy("assets/no-extension"), UNHASHED_CACHE_POLICY);
 }
@@ -232,6 +245,7 @@ fn a_hashed_asset_is_immutable_and_a_plain_one_is_not() {
 #[test]
 fn a_hash_is_recognised_by_its_shape() {
     // The bundler emits a mixed case base64 hash.
+    // 打包器输出的哈希是大小写混合的 base64。
     assert!(is_content_hashed("index-Vou83oaV.js"));
     assert!(is_content_hashed("style-CEH25aoZ.css"));
     assert!(is_content_hashed("app-deadbeef.js"));
@@ -270,6 +284,7 @@ fn post_to_a_get_route_is_refused() {
 #[test]
 fn a_crate_card_takes_the_first_sentence_only() {
     // The index shows what a crate is; the crate page shows the rest.
+    // 索引说明一个 crate 是什么；其余内容由 crate 页面呈现。
     assert_eq!(
         crate_summary_brief(
             "ApsisRS \u{7684}\u{5171}\u{4eab}\u{57fa}\u{7840}\u{7c7b}\u{578b}\u{3002}\u{672c} crate \u{4f4d}\u{4e8e}\u{4f9d}\u{8d56}\u{56fe}\u{7684}\u{5e95}\u{5c42}\u{3002}"
@@ -281,6 +296,7 @@ fn a_crate_card_takes_the_first_sentence_only() {
 #[test]
 fn a_number_is_not_a_sentence_end() {
     // A version or a measurement must not cut a sentence in half.
+    // 版本号或量值不得把句子截成两半。
     assert_eq!(
         crate_summary_brief("Reads version 1.5 of the format. Then it checksums."),
         "Reads version 1.5 of the format."
diff --git a/tests/docs_api.rs b/tests/docs_api.rs
index ff44ab0..72e73f0 100644
--- a/tests/docs_api.rs
+++ b/tests/docs_api.rs
@@ -1,10 +1,16 @@
 //! Tests for the interface catalog reader.
+//! 接口目录读取器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::docs::api::*;
 use apsis_book::testkit::parse_item;
 
@@ -46,6 +52,8 @@ fn malformed_input_yields_an_empty_catalog() {
 fn an_item_carries_both_languages() {
     // `apsis-rs` writes the doc comment in English and then in Chinese, and
     // the extractor separates the two into the catalogue.
+
+    // `apsis-rs` 把文档注释先写成英文、再写成中文，提取器把两者分开写入目录。
     let item = r#"{"kind":"fn","name":"new","doc":"English.",
             "doc_zh":"中文。","signature":"pub fn new()"}"#;
     let parsed = parse_item(
@@ -62,6 +70,8 @@ fn an_item_carries_both_languages() {
 fn an_item_without_a_translation_has_none() {
     // A comment that is English only leaves the Chinese empty, and the
     // reader is then shown the English rather than nothing.
+
+    // 只有英文的注释使中文一侧为空，此时读者看到的是英文，而不是什么都没有。
     let item = r#"{"kind":"fn","name":"new","doc":"English.",
             "signature":"pub fn new()"}"#;
     let parsed = parse_item(
@@ -78,6 +88,9 @@ fn the_committed_catalogue_carries_both_languages_for_every_item() {
     // The translation comes from the source doc comments rather than from a
     // file maintained beside them, so a crate that was never translated shows
     // up here rather than silently reading as English to a Chinese reader.
+
+    // 译文来自源码文档注释，而不是在它们旁边另行维护的文件，因此从未翻译过的
+    // crate 会在这里暴露出来，而不是悄悄以英文呈现给中文读者。
     let catalog = apsis_book::docs::load_api_catalog();
     let mut missing = Vec::new();
     for krate in &catalog.crates {
diff --git a/tests/docs_content.rs b/tests/docs_content.rs
index 406a30a..3034458 100644
--- a/tests/docs_content.rs
+++ b/tests/docs_content.rs
@@ -1,10 +1,16 @@
 //! Tests for the embedded content table.
+//! 内嵌内容表的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::docs::content::*;
 
 #[test]
diff --git a/tests/docs_document.rs b/tests/docs_document.rs
index e82e088..cc406db 100644
--- a/tests/docs_document.rs
+++ b/tests/docs_document.rs
@@ -1,10 +1,16 @@
 //! Tests for the document model and the search tokenizer.
+//! 文档模型与搜索分词的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::docs::document::*;
 use apsis_book::testkit::tokenise;
 
@@ -43,9 +49,11 @@ BSTAR 项。
 ";
 
 /// The layer the sample documents declare in the tests.
+/// 测试中的样例文档所声明的层。
 const LAYER: &str = "orbit";
 
 /// Parses the English sample under the given identifier.
+/// 以给定标识解析英文样例。
 fn sample(id: &str) -> Document {
     Document::parse(id, LAYER, Language::English, SAMPLE).expect("the sample must parse")
 }
@@ -68,6 +76,9 @@ fn a_repeated_top_level_title_is_dropped_from_the_body() {
     let document = sample("sgp4");
     // The sample body opens with `# SGP4`, which differs from the
     // metadata title `SGP4 propagation`, so it is kept.
+
+    // 样例正文以 `# SGP4` 开头，与元数据标题 `SGP4 propagation` 不同，
+    // 因此它被保留。
     assert!(document.english.html.contains("<h1"));
     assert!(
         document
@@ -78,6 +89,7 @@ fn a_repeated_top_level_title_is_dropped_from_the_body() {
     );
 
     // A body that repeats the metadata title loses the repeated heading.
+    // 重复元数据标题的正文会去掉那个重复的标题。
     let repeated = "---\ntitle: SGP4 propagation\n---\n\n# SGP4 propagation\n\nBody.\n";
     let variant = DocumentVariant::parse(repeated).expect("must parse");
     assert!(!variant.html.contains("<h1"));
@@ -95,18 +107,21 @@ fn a_translation_replaces_the_language_form() {
     let mut document = sample("sgp4");
     assert!(!document.has(Language::Chinese));
     // Before the translation the Chinese reader sees the English form.
+    // 译文之前，中文读者看到的是英文形式。
     assert_eq!(document.title(Language::Chinese), "SGP4 propagation");
     document.chinese = Some(DocumentVariant::parse(SAMPLE_ZH).expect("must parse"));
     assert!(document.has(Language::Chinese));
     assert_eq!(document.title(Language::Chinese), "SGP4 传播");
     assert_eq!(document.title(Language::English), "SGP4 propagation");
     // The references of either form are merged.
+    // 两种形式的引用被合并。
     assert_eq!(document.references(), vec!["tle"]);
 }
 
 #[test]
 fn rejects_a_document_without_a_title() {
     // Without a title the document cannot be listed.
+    // 没有标题的文档无法被列出。
     assert!(Document::parse("x", LAYER, Language::English, "---\nsummary: s\n---\nbody").is_none());
     assert!(DocumentVariant::parse("---\nsummary: s\n---\nbody").is_none());
 }
@@ -151,6 +166,8 @@ fn a_translated_document_is_indexed_in_both_languages() {
     assert_eq!(hits[0].language, Language::Chinese);
     // The English body contains "propagates", which the Chinese body
     // does not.
+
+    // 英文正文含有 "propagates"，中文正文没有。
     let hits = index.search("propagates", 5);
     assert_eq!(hits.len(), 1);
     assert_eq!(hits[0].language, Language::English);
@@ -163,8 +180,11 @@ fn tokenise_emits_words_and_han_pairs() {
     assert_eq!(tokenise("坐标"), vec!["坐标"]);
     // A lone Chinese character produces no token; the search falls back
     // to a substring match for it.
+
+    // 单个中文字符不产生词元；搜索对它回退到子串匹配。
     assert!(tokenise("轨").is_empty());
     // A single Latin character is dropped.
+    // 单个拉丁字符被丢弃。
     assert!(tokenise("a").is_empty());
 }
 
@@ -189,11 +209,14 @@ fn a_chinese_query_matches_a_word_inside_a_sentence() {
     let tree = Tree::new(documents);
     let index = tree.search_index();
     // A two character query matches the pair inside the sentence.
+    // 两字查询匹配句子内部的相邻字符对。
     let hits = index.search("坐标", 5);
     assert_eq!(hits.len(), 1);
     assert_eq!(hits[0].id, "a");
     // A one character query has no token and falls back to a substring
     // match.
+
+    // 单字查询没有词元，回退到子串匹配。
     let hits = index.search("轨", 5);
     assert_eq!(hits.len(), 1);
     assert_eq!(hits[0].id, "a");
@@ -236,6 +259,10 @@ fn a_document_is_offered_once_when_its_layer_has_subjects() {
     // them. If a document were also left in the layer's own list, the
     // page would render it twice under one key and stop rendering at
     // all, so no identifier may appear twice in the reading order.
+
+    // 物理层声明了两个子区，因此它的文档住在其中。若某篇文档同时留在层自己的
+    // 列表里，页面会在同一个键下渲染它两次而完全停止渲染，因此阅读顺序中任何
+    // 标识都不得出现两次。
     let documents = vec![
         Document::parse(
             "time-scales",
@@ -266,6 +293,7 @@ fn a_document_is_offered_once_when_its_layer_has_subjects() {
     );
 
     // Both documents are still reachable, each under exactly one layer.
+    // 两篇文档仍然可达，各自恰好属于一个层。
     let physics = tree
         .groups()
         .iter()
diff --git a/tests/docs_markdown.rs b/tests/docs_markdown.rs
index b3808d0..79917ca 100644
--- a/tests/docs_markdown.rs
+++ b/tests/docs_markdown.rs
@@ -1,10 +1,16 @@
 //! Tests for the Markdown renderer.
+//! Markdown 渲染器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::docs::markdown::*;
 
 #[test]
@@ -25,6 +31,7 @@ fn a_display_formula_is_rendered_on_its_own() {
 #[test]
 fn a_dollar_without_a_pair_is_left_alone() {
     // A price must survive as a price.
+    // 价格必须作为价格保留下来。
     let html = render("It costs $5 today.");
     assert!(html.contains("$5"), "the lone dollar was consumed");
     assert!(!html.contains("<math"), "no formula should be produced");
@@ -34,6 +41,8 @@ fn a_dollar_without_a_pair_is_left_alone() {
 fn two_prices_are_not_a_formula() {
     // The closing dollar has a space before it, which is what separates
     // this from a formula.
+
+    // 收尾的美元符号前有一个空格，这正是它与公式的区别所在。
     let html = render("It costs $5 and then $6.");
     assert!(
         !html.contains("<math"),
@@ -93,6 +102,7 @@ fn a_rust_path_link_points_at_the_interface_page() {
     assert!(html.contains("data-api=\"Epoch\""), "{html}");
     assert!(html.contains("href=\"#/api/Epoch\""), "{html}");
     // A web address is left as it is.
+    // 网址按原样保留。
     assert!(html.contains("href=\"https://example.com\""), "{html}");
 }
 
@@ -108,11 +118,13 @@ fn a_path_to_a_variant_resolves_to_the_declaring_item() {
     );
     assert!(html.contains("data-api=\"PropagationErrorKind\""), "{html}");
     // A path whose segments are all unknown is left as written.
+    // 所有片段都未知的路径按原样保留。
     let html = render_with("[`Nope`](crate::Unknown::Missing).\n", Some(&known));
     assert!(!html.contains("data-api"), "{html}");
 }
 
 /// The names of two items, for the shortcut link test.
+/// 两个条目的名字，供简写链接的测试使用。
 fn items() -> std::collections::HashSet<String> {
     ["mjd", "Epoch"]
         .iter()
@@ -131,10 +143,12 @@ fn a_shortcut_link_points_at_the_interface_page() {
     assert!(html.contains("href=\"#/api/mjd\""), "{html}");
     assert!(html.contains("data-api=\"Epoch\""), "{html}");
     // A label that is not an item name stays as a code span.
+    // 不是条目名的标签保持为代码片段。
     let html = render_with("The range is [`0, 1`].\n", Some(&known));
     assert!(!html.contains("data-api"), "{html}");
     assert!(html.contains("<code>0, 1</code>"), "{html}");
     // A name that is not in the catalog also stays as a code span.
+    // 不在目录中的名字同样保持为代码片段。
     let html = render_with("See [`NotAnItem`].\n", Some(&known));
     assert!(!html.contains("data-api"), "{html}");
 }
@@ -144,6 +158,9 @@ fn a_chinese_heading_keeps_its_own_anchor() {
     // Only ASCII letters were kept, so every Chinese heading reduced to
     // the fallback and the whole table of contents pointed at the first
     // section.
+
+    // 只保留了 ASCII 字母，于是每个中文标题都归约到同一个回退值，整份目录都指向
+    // 第一节。
     let html = render("# 时间尺度\n\n正文。\n\n# 单位约定\n\n更多。\n");
     assert!(html.contains("id=\"时间尺度\""), "{html}");
     assert!(html.contains("id=\"单位约定\""), "{html}");
@@ -192,6 +209,8 @@ fn plain_text_drops_the_markup() {
 fn plain_text_resolves_a_shortcut_reference() {
     // A rustdoc shortcut keeps the item name and loses the brackets,
     // which otherwise appear verbatim in a one line summary.
+
+    // rustdoc 简写保留条目名并去掉方括号，否则方括号会原样出现在一行摘要里。
     let text = to_plain_text("See [`Vec3`] and [`Epoch::mjd`](crate::Epoch::mjd).\n");
     assert!(text.contains("Vec3"));
     assert!(text.contains("mjd"));
diff --git a/tests/docs_mathml.rs b/tests/docs_mathml.rs
index 49d31be..8fd70d5 100644
--- a/tests/docs_mathml.rs
+++ b/tests/docs_mathml.rs
@@ -1,10 +1,16 @@
 //! Tests for the formula renderer.
+//! 公式渲染器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::docs::mathml::*;
 use apsis_book::testkit::mathml;
 
@@ -47,6 +53,9 @@ fn an_unknown_command_is_kept_as_written() {
     // Losing part of a formula would be worse than showing it plainly.
     // Text is given an element even when it is not understood, because text
     // without one is not drawn at all.
+
+    // 丢掉公式的一部分比把它朴素地显示出来更糟。即使用户未被理解，文本仍会被赋予
+    // 元素，因为没有元素的文本根本不会被绘制。
     assert_eq!(mathml("\\notacommand"), "<mtext>\\notacommand</mtext>");
 }
 
@@ -55,6 +64,9 @@ fn a_comma_is_kept() {
     // The command is the spacing one, so dropping it would run a list of
     // symbols together. It is written as an operator so that it keeps its
     // space, which is what a comma is for.
+
+    // 该命令是空格类命令，丢掉它会让一串符号挤在一起。它被写成运算符，从而保住
+    // 自己的空格——逗号正是为此而设。
     assert_eq!(
         mathml("\\alpha, \\beta"),
         "<mrow><mi>α</mi><mo>,</mo><mspace width=\"0.25em\"/><mi>β</mi></mrow>"
@@ -82,6 +94,7 @@ fn a_display_formula_is_marked_as_such() {
 #[test]
 fn the_source_is_kept_in_the_output() {
     // The page keeps the source so the formula can be copied back.
+    // 页面保留源码，使公式能被复制回去。
     assert!(render("x^2", false).contains("data-tex=\"x^2\""));
 }
 
@@ -90,6 +103,9 @@ fn a_bracketed_group_takes_the_power_that_follows_it() {
     // The bracket branches returned before the scripts were attached, so the
     // caret was set as an ordinary symbol and the exponent sat beside the
     // group: `(a + b)^2` showed its own caret.
+
+    // 括号分支在挂接上下标之前就返回了，于是脱字符被当作普通符号排版，指数则
+    // 落在括号组旁边：`(a + b)^2` 把自己的脱字符显示了出来。
     for latex in [
         r"(a + b)^2",
         r"\left( \frac{x_{ke}}{n_0} \right)^{2/3}",
@@ -109,6 +125,7 @@ fn a_bracketed_group_takes_the_power_that_follows_it() {
 }
 
 /// The MathML of a formula written in LaTeX.
+/// 以 LaTeX 书写的公式的 MathML。
 fn render_plain_of(latex: &str) -> String {
     apsis_book::docs::mathml::render(latex, false)
         .split("display=\"inline\">")
diff --git a/tests/embedded.rs b/tests/embedded.rs
index 589991a..afe6184 100644
--- a/tests/embedded.rs
+++ b/tests/embedded.rs
@@ -1,10 +1,16 @@
 //! Tests for access to the embedded frontend assets.
+//! 对内嵌前端资源的访问的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::embedded::*;
 
 #[test]
diff --git a/tests/formula_rendering.rs b/tests/formula_rendering.rs
index 39f15cc..69ede45 100644
--- a/tests/formula_rendering.rs
+++ b/tests/formula_rendering.rs
@@ -26,6 +26,26 @@
 //! as `\ln`, is drawn as those letters, so stripping every command only
 //! makes this check less strict about a function name and never hides a lost
 //! number.
+//!
+//! 比对公式显示的与它被书写的内容。
+//!
+//! 公式在文档中写成纯文本，再翻译为 MathML。翻译可能丢掉一个 token 而公式仍
+//! 在：结果看起来仍像公式，却是错的。这里就发生过——`year + 4800` 里的 4800
+//! 被写成行内裸文本，而浏览器不绘制它，于是渲染出的页面上所有多位数都不见了，
+//! 标记看起来却还算合理。
+//!
+//! 因此本检查针对字符而不是结构：源码中的每一个字母与数字都必须出现在页面会
+//! 显示的文本里。它遍历每一篇文档而不是抽取样本，因为该缺陷是逐个公式的，样本
+//! 会漏掉大部分。
+//!
+//! 只比对字母与数字。公式源码中的其他字符是记法而非内容：`^` 与 `_` 说明升降，
+//! `*` 表示相乘，`/` 表示相除，花括号用于分组。它们都应当从页面上消失，因为
+//! 排版已经表达了它们的意思。而数字或名字没有这样的借口，少一个就是缺陷。
+//!
+//! LaTeX 命令是同一类记法。`\sqrt` 被画成根号，`\Delta` 被画成希腊字母，
+//! 因此它们的字母本就消失，不算缺失。名字即其字形的命令，例如 `\ln`，就按那些
+//! 字母绘制，所以剥掉所有命令只会让本检查对函数名更宽松，而绝不会掩盖一个丢失
+//! 的数字。
 
 use apsis_book::docs::document::Language;
 
@@ -36,12 +56,20 @@ use apsis_book::docs::document::Language;
 /// version counted any text inside any element, which made the check below
 /// pass whatever the renderer produced: text with no element was counted as
 /// drawn although the browser shows nothing.
+///
+/// 返回读者看到的文本。
+///
+/// 浏览器绘制叶子元素内的文本，并丢弃没有元素包裹的文本，因此这里只按同样的
+/// 规则统计。早先的版本统计任何元素内部的文本，使下面的检查无论在渲染器产出
+/// 什么时都通过：没有元素的文本被算作已绘制，而浏览器什么也不显示。
 fn visible(html: &str) -> String {
     /// The elements whose text is drawn.
+    /// 其文本会被绘制的元素。
     const LEAF: [&str; 6] = ["mi", "mo", "mn", "mtext", "mspace", "ms"];
 
     let mut out = String::new();
     // The elements currently open, innermost last.
+    // 当前打开的元素，最内层在最后。
     let mut open: Vec<String> = Vec::new();
     let mut characters = html.chars().peekable();
     let mut in_tag = false;
@@ -70,6 +98,7 @@ fn visible(html: &str) -> String {
             _ if in_tag => tag.push(character),
             _ => {
                 // Drawn only when the innermost open element holds text.
+                // 只有当最内层打开的元素持有文本时才绘制。
                 if open
                     .last()
                     .is_some_and(|name| LEAF.contains(&name.as_str()))
@@ -89,12 +118,22 @@ fn visible(html: &str) -> String {
 /// its rows, and the braces that group. None of them is drawn as those
 /// characters, so none of them is expected on the page. What remains is the
 /// letters and digits, which are content and must all appear.
+///
+/// 返回公式源码中的内容字符。
+///
+/// 被剔除的是记法：命令名、环境名、分隔矩阵单元格的 `&` 与分隔各行的 `\\`，
+/// 以及用于分组的花括号。它们都不以这些字符的形式被绘制，因此都不应出现在
+/// 页面上。剩下的是字母与数字，它们是内容，必须全部出现。
 fn content_characters(source: &str) -> String {
     // The attribute is HTML escaped, so a cell separator arrives as `&amp;`
     // and would otherwise leave the letters of `amp` behind.
     // `sqrt` is written bare in the plain notation and with a backslash in
     // LaTeX; the bare form has to go as well, because it is drawn as a
     // radical sign rather than as its letters.
+
+    // 该属性经过 HTML 转义，因此单元格分隔符到手时是 `&amp;`，否则会留下
+    // `amp` 这几个字母。`sqrt` 在朴素记法中写成裸词、在 LaTeX 中带反斜杠；
+    // 裸词形式同样要去掉，因为它被绘制成根号而不是那些字母。
     let unescaped = source
         .replace("sqrt", "")
         .replace("&amp;", "&")
@@ -111,6 +150,10 @@ fn content_characters(source: &str) -> String {
             // The name is captured so that `begin` and `end` can be told
             // apart from the rest, because those two carry the name of an
             // environment in braces after them.
+
+            // 命令一直延伸到第一个非字母字符。名字被捕获下来，是为了把
+            // `begin` 与 `end` 同其余命令区分开——只有这两个会在其后用花括号
+            // 携带环境名。
             '\\' => {
                 let mut name = String::new();
                 while let Some(next) = characters.peek().copied() {
@@ -137,6 +180,7 @@ fn content_characters(source: &str) -> String {
 }
 
 /// Returns the formula sources of one document, in order.
+/// 按顺序返回一篇文档中的公式源码。
 fn formula_blocks(html: &str) -> Vec<String> {
     let mut found = Vec::new();
     let mut rest = html;
@@ -156,6 +200,7 @@ fn every_formula_shows_every_character_it_was_written_with() {
     let mut failures = Vec::new();
 
     // The concept documents, in both languages.
+    // 概念文档，含两种语言。
     let mut sources: Vec<(String, String)> = Vec::new();
     for document in &apsis_book::docs::load_documents() {
         for language in [Language::English, Language::Chinese] {
@@ -165,10 +210,15 @@ fn every_formula_shows_every_character_it_was_written_with() {
     // And the interface documentation, which carries formulas of its own in
     // the doc comments of the crate it describes. Leaving it out would have
     // hidden every formula there.
+
+    // 以及接口文档，它在其所描述的 crate 的文档注释中自带公式。把它排除在外会
+    // 让那里的每一个公式都无人检查。
     for krate in apsis_book::docs::load_api_catalog().crates {
         for item in &krate.items {
             // The doc comment is Markdown, and the service renders it with
             // the same renderer as a document.
+
+            // 文档注释是 Markdown，服务用与文档相同的渲染器渲染它。
             for text in [Some(&item.doc), item.doc_zh.as_ref()]
                 .into_iter()
                 .flatten()
@@ -188,11 +238,17 @@ fn every_formula_shows_every_character_it_was_written_with() {
                 checked += 1;
                 // The source as written, without the spaces that only set it
                 // out on the page.
+
+                // 源码按书写时的样子，去掉那些仅为页面排版而设的空格。
                 let written = content_characters(&source);
                 // The part of the page that is the formula itself: the
                 // MathML and nothing else. The source is carried beside it
                 // for a reader to copy, and including it here would compare
                 // the source against itself and pass whatever happened.
+
+                // 页面上属于公式本身的部分：MathML，别无其他。源码被携带在其旁
+                // 供读者复制，若把它算进来，就成了源码与自身比对，无论发生什么
+                // 都会通过。
                 let from = html.find(&format!("data-tex=\"{source}\"")).unwrap_or(0);
                 let start = html[from..].find("<math").map(|e| from + e).unwrap_or(from);
                 let end = html[start..]
@@ -207,6 +263,10 @@ fn every_formula_shows_every_character_it_was_written_with() {
                 // raise or lower, and neither is drawn. One that reaches the
                 // output is a script that was never attached, which leaves a
                 // formula that has every character in it and is still wrong.
+
+                // 脱字符与下划线是记法：它们说明升降，二者都不被绘制。出现在
+                // 输出里的那一个，说明有上下标从未被挂接，这会留下一个每个字符
+                // 都在、却依然是错的公式。
                 let body = &html[start..end];
                 for marker in ["<mo>^</mo>", "<mo>_</mo>"] {
                     assert!(
diff --git a/tests/graph.rs b/tests/graph.rs
index 21dde65..54263ee 100644
--- a/tests/graph.rs
+++ b/tests/graph.rs
@@ -1,10 +1,16 @@
 //! Tests for the graph model and the crate structure.
+//! 图模型与 crate 结构的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::graph::*;
 
 const SAMPLE: &str = r#"{
diff --git a/tests/http_request.rs b/tests/http_request.rs
index e7a52e3..a0522a9 100644
--- a/tests/http_request.rs
+++ b/tests/http_request.rs
@@ -1,10 +1,16 @@
 //! Tests for the request parser.
+//! 请求解析器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::http::request::*;
 
 use std::io::Cursor;
diff --git a/tests/http_response.rs b/tests/http_response.rs
index 46e6974..0ce60a2 100644
--- a/tests/http_response.rs
+++ b/tests/http_response.rs
@@ -1,10 +1,16 @@
 //! Tests for the response writer.
+//! 响应写出器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::http::response::*;
 
 #[test]
@@ -33,6 +39,9 @@ fn empty_body_has_no_content_type() {
     let text = String::from_utf8(response.to_bytes()).unwrap();
     // The response carries `X-Content-Type-Options`, so the assertion is
     // on the leading header line rather than on the substring.
+
+    // 响应带有 `X-Content-Type-Options`，因此断言落在起始的那一行首部上，
+    // 而不是落在子串上。
     assert!(!text.contains("\r\nContent-Type:"));
     assert!(text.contains("Content-Length: 0\r\n"));
 }
diff --git a/tests/http_server.rs b/tests/http_server.rs
index 82ffd09..b7f5d7d 100644
--- a/tests/http_server.rs
+++ b/tests/http_server.rs
@@ -1,9 +1,15 @@
 //! Tests for the listener and the worker pool.
+//! 监听器与工作线程池的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use apsis_book::http::request::{Request, RequestError};
 use apsis_book::http::response::{Response, Status};
 use std::net::SocketAddr;
@@ -45,6 +51,7 @@ fn serves_a_request_over_a_real_socket() {
 
     drop(stream);
     // The accept loop ends when the listener is dropped with the thread.
+    // 接受循环在线程随监听器一同被丢弃时结束。
     let _ = running;
 }
 
diff --git a/tests/i18n.rs b/tests/i18n.rs
index 9b31e93..c60bc59 100644
--- a/tests/i18n.rs
+++ b/tests/i18n.rs
@@ -1,10 +1,16 @@
 //! Tests for the bilingual strings.
+//! 双语字符串的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::i18n::*;
 
 use apsis_book::json;
diff --git a/tests/json_codec.rs b/tests/json_codec.rs
index 5fd0913..fae5bba 100644
--- a/tests/json_codec.rs
+++ b/tests/json_codec.rs
@@ -1,9 +1,15 @@
 //! Tests for the JSON codec.
+//! JSON 编解码器的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use apsis_book::testkit::json_object;
 
 use apsis_book::json::*;
diff --git a/tests/service.rs b/tests/service.rs
index 48b2b3c..dda27c2 100644
--- a/tests/service.rs
+++ b/tests/service.rs
@@ -8,6 +8,15 @@
 //! The binary is located through the `CARGO_BIN_EXE_apsis-book` variable that
 //! cargo sets for an integration test, so the test always runs against the
 //! binary built from the same sources.
+//!
+//! 针对服务二进制的端到端测试。
+//!
+//! 测试在一个临时端口上启动真实的二进制，等待它报告自己的地址，然后以普通 TCP
+//! 请求与之通信。这样把请求解析器、路由器、JSON 编解码器、内嵌内容与工具处理
+//! 函数放在一起检验，这是单元测试做不到的。
+//!
+//! 二进制的位置取自 cargo 为集成测试设置的 `CARGO_BIN_EXE_apsis-book`，因此测试
+//! 总是针对由同一份源码构建出的二进制运行。
 
 use std::io::{BufRead, BufReader, Read, Write};
 use std::net::TcpStream;
@@ -17,6 +26,7 @@ use std::thread;
 use std::time::{Duration, Instant};
 
 /// A running service that is stopped when it is dropped.
+/// 一个运行中的服务，被丢弃时即停止。
 struct Service {
     child: Child,
     address: String,
@@ -24,6 +34,7 @@ struct Service {
 
 impl Service {
     /// Starts the binary and waits for it to report its address.
+    /// 启动二进制并等待它报告自己的地址。
     fn start() -> Self {
         let mut child = Command::new(env!("CARGO_BIN_EXE_apsis-book"))
             .args(["--address", "127.0.0.1:0", "--workers", "2"])
@@ -51,6 +62,7 @@ impl Service {
     }
 
     /// Sends a raw request and returns the whole response as text.
+    /// 发送一个原始请求，并把整个响应作为文本返回。
     fn request(&self, request: &str) -> String {
         let mut stream =
             TcpStream::connect(&self.address).expect("the service must accept a connection");
@@ -68,11 +80,13 @@ impl Service {
     }
 
     /// Sends a GET request.
+    /// 发送一个 GET 请求。
     fn get(&self, path: &str) -> String {
         self.request(&format!("GET {path} HTTP/1.1\r\nHost: localhost\r\n\r\n"))
     }
 
     /// Sends a POST request with a JSON body.
+    /// 发送一个带 JSON 请求体的 POST 请求。
     fn post(&self, path: &str, body: &str) -> String {
         self.request(&format!(
             "POST {path} HTTP/1.1\r\nHost: localhost\r\nContent-Type: application/json\r\nContent-Length: {}\r\n\r\n{body}",
@@ -89,6 +103,7 @@ impl Drop for Service {
 }
 
 /// Returns the body of a response.
+/// 返回某个响应的请求体。
 fn body(response: &str) -> &str {
     response
         .split_once("\r\n\r\n")
@@ -97,6 +112,7 @@ fn body(response: &str) -> &str {
 }
 
 /// Returns the status line of a response.
+/// 返回某个响应的状态行。
 fn status(response: &str) -> &str {
     response.lines().next().unwrap_or("")
 }
@@ -105,6 +121,10 @@ fn status(response: &str) -> &str {
 ///
 /// The accept loop starts a moment after the address is printed, so the
 /// first connection can be refused.
+///
+/// 等待某个条件，轮询直到它成立或超过时限。
+///
+/// 接受循环在地址打印之后片刻才启动，因此第一次连接可能被拒绝。
 fn wait_ready(service: &Service) {
     let deadline = Instant::now() + Duration::from_secs(10);
     while Instant::now() < deadline {
@@ -152,6 +172,7 @@ fn serves_the_document_index_and_a_document() {
     let listing = body(&index);
     assert!(listing.contains("\"groups\""), "{listing}");
     // The concepts and the implementation are separate groups.
+    // 概念与实现是两个分开的分组。
     assert!(listing.contains("\"concepts\""), "{listing}");
     assert!(listing.contains("\"implementation\""), "{listing}");
 
@@ -185,15 +206,19 @@ fn interface_documentation_is_translated() {
     let item = service.get("/api/api/items/propagate_minutes");
     let body = body(&item);
     // The Chinese documentation is served and is rendered to HTML.
+    // 中文文档会被提供，并渲染为 HTML。
     assert!(body.contains("传播"), "the Chinese doc should be served");
     assert!(body.contains("<p>"), "the doc should be rendered as HTML");
     // A doc comment link to another item becomes an internal route.
+    // 指向另一个条目的文档注释链接会成为一个内部路由。
     assert!(
         body.contains("data-api=") && body.contains("#/api/"),
         "the doc link should be resolved: {body}"
     );
     // The English documentation is still present, so the language can switch
     // without another request.
+
+    // 英文文档仍然存在，因此切换语言无需再一次请求。
     assert!(
         body.contains("Returns the state of the satellite"),
         "the English doc should still be present"
@@ -207,6 +232,7 @@ fn crate_summaries_are_translated() {
     let response = service.get("/api/api/crates/apsis-sgp4");
     let body = body(&response);
     // The Chinese summary and its plain form are both served.
+    // 中文概要与它的纯文本形式都会被提供。
     assert!(
         body.contains("传播器"),
         "the Chinese summary should be served"
@@ -301,6 +327,7 @@ fn rejects_a_malformed_body_without_failing() {
     let body = body(&response);
     assert!(body.contains("\"ok\":false"), "{body}");
     // The service must still answer a subsequent request.
+    // 服务必须仍能回应后续请求。
     assert!(status(&service.get("/health")).contains("200"));
 }
 
@@ -321,6 +348,7 @@ fn documents_are_served_in_both_languages() {
     assert!(body.contains("\"language\":\"zh\""), "{body}");
     assert!(body.contains("\"language\":\"en\""), "{body}");
     // The Chinese form of the document carries Chinese text.
+    // 文档的中文形式携带中文文本。
     assert!(body.contains("传播"), "the Chinese form should be embedded");
 }
 
@@ -372,6 +400,8 @@ fn the_flow_index_lists_every_flow() {
     assert!(body.contains("tle-parsing"), "{body}");
     // The index carries a bilingual title, so the frontend needs no copy of
     // the flow names.
+
+    // 索引携带双语标题，因此前端无须另存一份流程图名。
     assert!(body.contains("\"title\""), "{body}");
     assert!(body.contains("\"zh\""), "{body}");
 }
@@ -382,6 +412,8 @@ fn static_assets_are_revalidated() {
     wait_ready(&service);
     // The build writes stable file names, so an immutable policy would pin a
     // reader to the bundle current at first load.
+
+    // 构建写出的是稳定的文件名，因此不可变策略会把读者钉在首次加载时的那个包上。
     let asset = service.get("/assets/app.js");
     assert!(asset.contains("no-cache"), "{asset}");
     assert!(!asset.contains("immutable"), "{asset}");
diff --git a/tests/state.rs b/tests/state.rs
index 40f1f63..5ad0820 100644
--- a/tests/state.rs
+++ b/tests/state.rs
@@ -1,10 +1,16 @@
 //! Tests for the parsed content shared by the workers.
+//! 各工作线程共享的已解析内容的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::state::*;
 
 #[test]
diff --git a/tests/tools_handlers.rs b/tests/tools_handlers.rs
index d683f65..af71f57 100644
--- a/tests/tools_handlers.rs
+++ b/tests/tools_handlers.rs
@@ -1,9 +1,15 @@
 //! Tests for the tool handlers.
+//! 工具处理函数的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use apsis_book::testkit::json_object;
 
 use apsis_book::tools::ToolError;
@@ -13,6 +19,7 @@ use apsis_book::json::Value;
 use apsis_book::tools::{Params, Registry};
 
 /// Runs a tool with the given parameters.
+/// 以给定参数运行一个工具。
 fn call(id: &str, values: Value) -> Result<Value, ToolError> {
     let registry = Registry::new();
     let tool = registry.get(id).unwrap();
@@ -21,11 +28,13 @@ fn call(id: &str, values: Value) -> Result<Value, ToolError> {
 }
 
 /// Returns the English text of a label, which is a bilingual object.
+/// 返回某个标签的英文文本，该标签是一个双语对象。
 fn label_english(value: &Value) -> &str {
     value.get("en").and_then(Value::as_str).unwrap_or("")
 }
 
 /// Returns the numeric value of the scalar with an English label.
+/// 返回英文标签为给定值的那个标量的数值。
 fn scalar_number(value: &Value, label: &str) -> f64 {
     value
         .get("scalars")
@@ -111,6 +120,8 @@ fn kepler_conversion_rejects_a_non_elliptical_orbit() {
     // An eccentricity of one is a parabola; the conversion requires an
     // ellipse, so the tool reports the condition without naming a
     // parameter.
+
+    // 偏心率为一即抛物线；该转换要求椭圆，因此工具报告该条件而不指名某个参数。
     let error = call(
         "kepler-state",
         json_object! { "eccentricity" => 1.0, "semi_major_axis" => 7000.0 },
diff --git a/tests/tools_labels.rs b/tests/tools_labels.rs
index 1c6feb8..ad1404f 100644
--- a/tests/tools_labels.rs
+++ b/tests/tools_labels.rs
@@ -1,10 +1,16 @@
 //! Tests for the tool result label table.
+//! 工具结果标签表的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
 
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
+
 use apsis_book::tools::labels::*;
 
 #[test]
diff --git a/tests/tools_out.rs b/tests/tools_out.rs
index c9834f7..b51b16c 100644
--- a/tests/tools_out.rs
+++ b/tests/tools_out.rs
@@ -1,15 +1,22 @@
 //! Tests for the tool result shape.
+//! 工具结果形状的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use apsis_book::json::Value;
 
 use apsis_book::tools::labels;
 use apsis_book::tools::out::*;
 
 /// The first cell of the first row of a shaped response.
+/// 某个已整形响应中第一行第一格的单元格。
 fn first_cell(value: &Value) -> Value {
     let rows = value
         .get("table")
@@ -26,6 +33,8 @@ fn first_cell(value: &Value) -> Value {
 fn a_text_cell_is_shown_in_either_language() {
     // The meaning of a field is a fixed phrase, so it is looked up rather
     // than written twice.
+
+    // 字段的含义是固定短语，因此走查表而不是写两遍。
     let mut table = Table::new(vec![Column::text("meaning", "Meaning")]);
     table.push(vec![Value::from("Mean motion")]);
     let value = table_response(
@@ -45,6 +54,9 @@ fn a_text_cell_is_shown_in_either_language() {
 fn an_identifier_is_not_set_as_a_formula() {
     // `mean_motion` is a field name. Set as a formula it would come out as
     // separate letters with a subscript, which is not the field name.
+
+    // `mean_motion` 是一个字段名。当成公式排版会变成逐字母加下标，那就不是
+    // 字段名了。
     let mut table = Table::new(vec![Column::text("field", "Field")]);
     table.push(vec![Value::from("mean_motion")]);
     let value = table_response("kind", "Title", Vec::new(), &table, Vec::new(), Vec::new());
@@ -58,6 +70,7 @@ fn an_identifier_is_not_set_as_a_formula() {
 #[test]
 fn a_unit_with_a_power_is_rendered() {
     // `rev/day^2` is a unit, and the power is what a reader needs raised.
+    // `rev/day^2` 是一个单位，读者需要看到的是被抬起的幂次。
     let mut table = Table::new(vec![Column::text("unit", "Unit")]);
     table.push(vec![Value::from("rev/day^2")]);
     let value = table_response("kind", "Title", Vec::new(), &table, Vec::new(), Vec::new());
diff --git a/tests/tools_registry.rs b/tests/tools_registry.rs
index 15c0ce9..728ebdc 100644
--- a/tests/tools_registry.rs
+++ b/tests/tools_registry.rs
@@ -1,9 +1,15 @@
 //! Tests for the tool registry.
+//! 工具注册表的测试。
 //!
 //! They live here rather than inside the module so that `src/` holds no test
 //! code, as it does in `apsis-rs`. An integration test is a separate crate and
 //! reaches only what the library makes public, so the few internal items the
 //! tests need are opened through `apsis_book::testkit`.
+
+//!
+//! 它们放在这里而不是模块内部，使 `src/` 不含测试代码，与 `apsis-rs` 一致。
+//! 集成测试是独立的 crate，只能触达库公开的部分，因此测试所需的那少数内部条目
+//! 经 `apsis_book::testkit` 开放。
 use apsis_book::testkit::json_object;
 
 use apsis_book::tools::*;