termdiff 4.2.1

Write a diff with color codes to a string
Documentation 
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//! Tests for algorithm selection and feature-gated availability.
//!
//! When both `myers` and `similar` features are enabled, the parity tests
//! verify they produce identical output. When only one is enabled, the
//! availability tests confirm the other gracefully falls back.
//!
//! Every test here renders through `ArrowsTheme`, so the whole file is skipped
//! when the `arrows` feature is disabled.
#![cfg(feature = "arrows")]

// ---------------------------------------------------------------------------
// Myers vs Similar output parity (requires both features)
// ---------------------------------------------------------------------------

#[cfg(all(feature = "myers", feature = "similar"))]
mod parity {
    use termdiff::{Algorithm, DrawDiff};

    /// Helper: render a diff with a specific algorithm.
    fn render_with(old: &str, new: &str, algorithm: Algorithm) -> String {
        use termdiff::ArrowsTheme;
        format!(
            "{}",
            DrawDiff::with_algorithm(old, new, &ArrowsTheme::default(), algorithm)
        )
    }

    #[test]
    fn simple_change() {
        let old = "The quick brown fox";
        let new = "The quick red fox";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }

    #[test]
    fn multiline_interleaved() {
        let old = "Line 1\nLine 2\nLine 3\nLine 4";
        let new = "Line 1\nModified Line 2\nLine 3\nModified Line 4";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }

    #[test]
    fn added_lines() {
        let old = "Line 1\nLine 3";
        let new = "Line 1\nLine 2\nLine 3";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }

    #[test]
    fn removed_lines() {
        let old = "Line 1\nLine 2\nLine 3";
        let new = "Line 1\nLine 3";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }

    #[test]
    fn trailing_newline() {
        let old = "Line 1\nLine 2\n";
        let new = "Line 1\nLine 2";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }

    #[test]
    fn empty_inputs() {
        assert_eq!(
            render_with("", "", Algorithm::Similar),
            render_with("", "", Algorithm::Myers),
        );
    }

    #[test]
    fn completely_different() {
        let old = "This is completely different";
        let new = "From this text";
        assert_eq!(
            render_with(old, new, Algorithm::Similar),
            render_with(old, new, Algorithm::Myers),
        );
    }
}

// ---------------------------------------------------------------------------
// Feature availability — only one algorithm enabled
// ---------------------------------------------------------------------------

#[cfg(all(feature = "myers", not(feature = "similar")))]
mod only_myers {
    use std::io::Cursor;

    use termdiff::{diff_with_algorithm, Algorithm};

    #[test]
    fn available() {
        use termdiff::ArrowsTheme;
        let old = "The quick brown fox";
        let new = "The quick red fox";
        let theme = ArrowsTheme::default();

        // Myers should work directly
        let mut buf = Cursor::new(Vec::new());
        diff_with_algorithm(&mut buf, old, new, &theme, Algorithm::Myers).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("<The quick brown fox"));
        assert!(output.contains(">The quick red fox"));

        // Similar should fall back to an available algorithm
        let mut buf = Cursor::new(Vec::new());
        diff_with_algorithm(&mut buf, old, new, &theme, Algorithm::Similar).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("<The quick brown fox"));
        assert!(output.contains(">The quick red fox"));
    }
}

#[cfg(all(feature = "similar", not(feature = "myers")))]
mod only_similar {
    use std::io::Cursor;

    use termdiff::{diff_with_algorithm, Algorithm};

    #[test]
    fn available() {
        use termdiff::ArrowsTheme;
        let old = "The quick brown fox";
        let new = "The quick red fox";
        let theme = ArrowsTheme::default();

        // Similar should work directly
        let mut buf = Cursor::new(Vec::new());
        diff_with_algorithm(&mut buf, old, new, &theme, Algorithm::Similar).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("<The quick brown fox"));
        assert!(output.contains(">The quick red fox"));

        // Myers should fall back to an available algorithm
        let mut buf = Cursor::new(Vec::new());
        diff_with_algorithm(&mut buf, old, new, &theme, Algorithm::Myers).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("<The quick brown fox"));
        assert!(output.contains(">The quick red fox"));
    }
}

// ---------------------------------------------------------------------------
// No algorithms available
// ---------------------------------------------------------------------------

#[cfg(not(any(feature = "myers", feature = "similar")))]
mod none {
    use std::io::Cursor;

    use termdiff::{diff, diff_with_algorithm, Algorithm};

    #[test]
    fn shows_error() {
        use termdiff::ArrowsTheme;
        let theme = ArrowsTheme::default();

        // diff() should produce the error message
        let mut buf = Cursor::new(Vec::new());
        diff(&mut buf, "old", "new", &theme).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("Error: No diff algorithms are available"));

        // diff_with_algorithm should also produce the error
        let mut buf = Cursor::new(Vec::new());
        diff_with_algorithm(&mut buf, "old", "new", &theme, Algorithm::Myers).unwrap();
        let output = String::from_utf8(buf.into_inner()).expect("Not valid UTF-8");
        assert!(output.contains("Error: No diff algorithms are available"));
    }
}