102 lines
3.6 KiB
Rust
102 lines
3.6 KiB
Rust
//! Tests for the decibel scale.
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//!
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//! 分贝尺度的测试。
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use apsis_rf::Decibel;
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const TOLERANCE: f64 = 1e-12;
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#[test]
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fn unity_and_doubling_have_the_expected_readings() {
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assert_eq!(Decibel::UNITY.db(), 0.0);
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assert!((Decibel::UNITY.ratio() - 1.0).abs() < TOLERANCE);
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// Three decibels is a ratio of 1.9953, not exactly two, which is the
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// reason the doubling constant is an approximation in practice.
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// 三分贝是 1.9953 的比而非恰好二，这正是加倍常量在实践中是近似的原因。
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assert!((Decibel::DOUBLING.db() - 3.010_299_956_639_812).abs() < TOLERANCE);
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assert!((Decibel::DOUBLING.ratio() - 2.0).abs() < TOLERANCE);
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}
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#[test]
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fn ratio_and_reading_round_trip() {
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for reading in [-30.0, -10.0, -3.0, 0.0, 1.5, 10.0, 30.0, 100.0] {
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let value = Decibel::from_db(reading);
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let ratio = value.ratio();
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let recovered = Decibel::from_ratio(ratio).expect("ratio is positive");
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assert!((recovered.db() - reading).abs() < 1e-9, "reading {reading}");
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}
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}
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#[test]
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fn a_ratio_of_ten_is_ten_decibels() {
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assert!((Decibel::from_ratio(10.0).expect("positive").db() - 10.0).abs() < TOLERANCE);
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assert!((Decibel::from_ratio(100.0).expect("positive").db() - 20.0).abs() < TOLERANCE);
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assert!((Decibel::from_ratio(0.001).expect("positive").db() + 30.0).abs() < TOLERANCE);
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}
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#[test]
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fn amplitude_ratios_use_twenty_per_decade() {
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// A voltage ratio of ten is twenty decibels, because power is
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// proportional to the square of the amplitude.
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// 电压比十即二十分贝，因为功率与幅度的平方成正比。
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let value = Decibel::from_amplitude_ratio(10.0).expect("positive");
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assert!((value.db() - 20.0).abs() < TOLERANCE);
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assert!((value.amplitude_ratio() - 10.0).abs() < 1e-9);
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}
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#[test]
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fn non_positive_ratios_are_rejected() {
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assert_eq!(Decibel::from_ratio(0.0), None);
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assert_eq!(Decibel::from_ratio(-1.0), None);
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assert_eq!(Decibel::from_ratio(f64::NAN), None);
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assert_eq!(Decibel::from_ratio(f64::INFINITY), None);
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assert_eq!(Decibel::from_amplitude_ratio(0.0), None);
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}
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#[test]
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fn addition_multiplies_the_ratio() {
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// The exact doubling constant added to itself quadruples the ratio.
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// 精确的加倍常量自加使其比变为四倍。
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let total = Decibel::DOUBLING + Decibel::DOUBLING;
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assert!((total.ratio() - 4.0).abs() < 1e-9);
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// Two ten decibel gains make a gain of one hundred.
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// 两个十分贝增益合成一百倍增益。
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let decades = Decibel::from_db(10.0) + Decibel::from_db(10.0);
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assert!((decades.db() - 20.0).abs() < TOLERANCE);
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assert!((decades.ratio() - 100.0).abs() < 1e-9);
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}
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#[test]
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fn subtraction_divides_the_ratio() {
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let net = Decibel::from_db(10.0) - Decibel::from_db(3.0);
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assert!((net.db() - 7.0).abs() < TOLERANCE);
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let ratio = Decibel::from_db(10.0).ratio() / Decibel::from_db(3.0).ratio();
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assert!((net.ratio() - ratio).abs() < 1e-9);
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}
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#[test]
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fn negation_inverts_the_ratio() {
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let value = Decibel::from_db(7.5);
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assert!((-value).db() + value.db() < TOLERANCE);
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assert!(((-value).ratio() * value.ratio() - 1.0).abs() < 1e-12);
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assert_eq!((-value).db(), value.negated().db());
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}
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#[test]
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fn finiteness_is_reported() {
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assert!(Decibel::from_db(1.0).is_finite());
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assert!(!Decibel::from_db(f64::INFINITY).is_finite());
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assert!(!Decibel::from_db(f64::NAN).is_finite());
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}
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#[test]
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fn display_includes_the_unit() {
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assert_eq!(Decibel::from_db(3.5).to_string(), "3.5 dB");
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}
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#[test]
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fn default_is_unity() {
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assert_eq!(Decibel::default(), Decibel::UNITY);
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}
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