feat: implement Not expectation combinator and revise failure messages

Author: haraldmaida

src/bigdecimal/tests.rs

@@ -27,7 +27,7 @@ fn verify_bigdecimal_is_equal_to_other_fails() {
     assert_eq!(
         failures,
         &[
-            r"assertion failed: expected subject is equal to BigDecimal(sign=Minus, scale=3, digits=[42831])
+            r"assertion failed: expected subject to be equal to BigDecimal(sign=Minus, scale=3, digits=[42831])
    but was: BigDecimal(sign=Plus, scale=3, digits=[42831])
   expected: BigDecimal(sign=Minus, scale=3, digits=[42831])
 "
@@ -181,7 +181,7 @@ fn verify_bigdecimalref_is_equal_to_other_fails() {
     assert_eq!(
         failures,
         &[
-            r"assertion failed: expected subject is equal to BigDecimalRef { sign: Minus, digits: 42831, scale: 3 }
+            r"assertion failed: expected subject to be equal to BigDecimalRef { sign: Minus, digits: 42831, scale: 3 }
    but was: BigDecimalRef { sign: Plus, digits: 42831, scale: 3 }
   expected: BigDecimalRef { sign: Minus, digits: 42831, scale: 3 }
 "

src/boolean/mod.rs

@@ -3,7 +3,7 @@
 use crate::assertions::AssertBoolean;
 use crate::colored::{mark_missing, mark_unexpected};
 use crate::expectations::{IsFalse, IsTrue};
-use crate::spec::{DiffFormat, Expectation, Expression, FailingStrategy, Spec};
+use crate::spec::{DiffFormat, Expectation, Expression, FailingStrategy, Invertible, Spec};
 use crate::std::format;
 use crate::std::string::String;
 
@@ -25,30 +25,46 @@ impl Expectation<bool> for IsTrue {
         *subject
     }
 
-    fn message(&self, expression: &Expression<'_>, actual: &bool, format: &DiffFormat) -> String {
-        let marked_actual = mark_unexpected(actual, format);
-        let marked_expected = mark_missing(&true, format);
+    fn message(
+        &self,
+        expression: &Expression<'_>,
+        actual: &bool,
+        inverted: bool,
+        format: &DiffFormat,
+    ) -> String {
+        let marked_actual = mark_unexpected(&actual, format);
+        let marked_expected = mark_missing(&!inverted, format);
         format!(
-            "expected {expression} is {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
+            "expected {expression} to be {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
             true
         )
     }
 }
 
+impl Invertible for IsTrue {}
+
 impl Expectation<bool> for IsFalse {
     fn test(&mut self, subject: &bool) -> bool {
         !*subject
     }
 
-    fn message(&self, expression: &Expression<'_>, actual: &bool, format: &DiffFormat) -> String {
+    fn message(
+        &self,
+        expression: &Expression<'_>,
+        actual: &bool,
+        inverted: bool,
+        format: &DiffFormat,
+    ) -> String {
         let marked_actual = mark_unexpected(actual, format);
-        let marked_expected = mark_missing(&false, format);
+        let marked_expected = mark_missing(&inverted, format);
         format!(
-            "expected {expression} is {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
+            "expected {expression} to be {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
             false
         )
     }
 }
 
+impl Invertible for IsFalse {}
+
 #[cfg(test)]
 mod tests;

src/boolean/tests.rs

@@ -23,10 +23,12 @@ fn verify_bool_is_not_equal_to_false_fails() {
 
     assert_eq!(
         failures,
-        &[r"assertion failed: expected my_thing is not equal to false
+        &[
+            r"assertion failed: expected my_thing to be not equal to false
    but was: false
   expected: not false
-"]
+"
+        ]
     );
 }
 
@@ -47,7 +49,7 @@ fn verify_bool_is_true_fails() {
             .named("my_thing")
             .is_true()
             .display_failures(),
-        &[r"assertion failed: expected my_thing is true
+        &[r"assertion failed: expected my_thing to be true
    but was: false
   expected: true
 "]
@@ -63,7 +65,7 @@ fn verify_bool_is_false_fails() {
 
     assert_eq!(
         failures,
-        &[r"assertion failed: expected my_thing is false
+        &[r"assertion failed: expected my_thing to be false
    but was: true
   expected: false
 "]
@@ -83,7 +85,7 @@ mod colored {
 
         assert_eq!(
             failures,
-            &["assertion failed: expected subject is true\n   \
+            &["assertion failed: expected subject to be true\n   \
                but was: \u{1b}[31mfalse\u{1b}[0m\n  \
               expected: \u{1b}[32mtrue\u{1b}[0m\n\
             "]
@@ -99,7 +101,7 @@ mod colored {
 
         assert_eq!(
             failures,
-            &["assertion failed: expected subject is false\n   \
+            &["assertion failed: expected subject to be false\n   \
                but was: \u{1b}[31mtrue\u{1b}[0m\n  \
               expected: \u{1b}[33mfalse\u{1b}[0m\n\
             "]