xpct 0.5.1

An extensible test assertion library
Documentation 
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use std::marker::PhantomData;

use crate::core::{style, Format, Formatter, MatchFailure, Matcher, NegFormat};
use crate::matchers::boolean::BeTrueMatcher;

/// A formatter which prints a static string message.
///
/// Use this over [`Expectation`] when there's no point including the actual value in the output. A
/// good example of this is the [`be_true`] matcher, where if the matcher failed, you know the
/// actual value must be `false`.
///
/// # Examples
///
/// ```
/// # use xpct::format::MessageFormat;
/// let format: MessageFormat = MessageFormat::new(
///     "Expected this to be true",
///     "Expected this to be false"
/// );
/// ```
///
/// [`Expectation`]: crate::matchers::Expectation
/// [`be_true`]: crate::be_true
#[derive(Debug)]
pub struct MessageFormat<PosFail = (), NegFail = ()> {
    marker: PhantomData<(PosFail, NegFail)>,
    pos_msg: String,
    neg_msg: String,
}

impl<PosFail, NegFail> MessageFormat<PosFail, NegFail> {
    /// Create a new [`MessageFormat`].
    ///
    /// This accepts two error messages: the one to use in the *positive* case (when we were
    /// expecting the matcher to succeed) and the one to use in the *negative* case (when we were
    /// expecting the matcher to fail).
    pub fn new(pos_msg: impl Into<String>, neg_msg: impl Into<String>) -> Self {
        Self {
            marker: PhantomData,
            pos_msg: pos_msg.into(),
            neg_msg: neg_msg.into(),
        }
    }
}

impl<PosFail, NegFail> Format for MessageFormat<PosFail, NegFail> {
    type Value = MatchFailure<PosFail, NegFail>;

    fn fmt(&self, f: &mut Formatter, value: Self::Value) -> crate::Result<()> {
        f.set_style(style::bad());
        if value.is_pos() {
            f.write_str(&self.pos_msg);
        } else {
            f.write_str(&self.neg_msg);
        }
        f.reset_style();
        f.write_char('\n');

        Ok(())
    }
}

fn bool_format() -> MessageFormat {
    MessageFormat::new("Expected this to be true", "Expected this to be false")
}

/// Succeeds when the actual value is `true`.
///
/// # Examples
///
/// ```
/// use xpct::{expect, be_true};
///
/// expect!(true).to(be_true());
/// expect!(false).to_not(be_true());
/// ```
pub fn be_true() -> Matcher<'static, bool, bool> {
    Matcher::new(BeTrueMatcher::new(), bool_format())
}

/// Succeeds when the actual value is `false`.
///
/// # Examples
///
/// ```
/// use xpct::{expect, be_false};
///
/// expect!(false).to(be_false());
/// expect!(true).to_not(be_false());
/// ```
pub fn be_false() -> Matcher<'static, bool, bool> {
    Matcher::neg(BeTrueMatcher::new(), NegFormat(bool_format()))
}

#[cfg(test)]
mod tests {
    use super::{be_false, be_true};
    use crate::expect;

    #[test]
    fn succeeds_when_true() {
        expect!(true).to(be_true());
    }

    #[test]
    fn succeeds_when_not_true() {
        expect!(false).to_not(be_true());
    }

    #[test]
    #[should_panic]
    fn fails_when_true() {
        expect!(true).to_not(be_true());
    }

    #[test]
    #[should_panic]
    fn fails_when_not_true() {
        expect!(false).to(be_true());
    }

    #[test]
    fn succeeds_when_false() {
        expect!(false).to(be_false());
    }

    #[test]
    fn succeeds_when_not_false() {
        expect!(true).to_not(be_false());
    }

    #[test]
    #[should_panic]
    fn fail_when_false() {
        expect!(false).to_not(be_false());
    }

    #[test]
    #[should_panic]
    fn fails_when_not_false() {
        expect!(true).to(be_false());
    }
}