Highlighting differences between expected and actual value

.github/workflows/ci.yml

@@ -93,7 +93,7 @@ jobs:
         uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --no-default-features --features "float"
+          args: --no-default-features --features "colored, float"
 
   msrv:
     name: Build with MSRV

.ide-settings/jetbrains/runConfigurations/Clippy no-features.run.xml

@@ -0,0 +1,19 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Clippy no-features" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="command" value="clippy --all-targets --no-default-features" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="false" />
+    <option name="allFeatures" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="NO" />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.ide-settings/jetbrains/runConfigurations/Clippy no-std.run.xml

@@ -1,6 +1,6 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="Clippy no-std" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
-    <option name="command" value="clippy --all-targets --no-default-features" />
+    <option name="command" value="clippy --all-targets --no-default-features --features &quot;colored, float&quot;" />
     <option name="workingDirectory" value="file://$PROJECT_DIR$" />
     <envs />
     <option name="emulateTerminal" value="false" />

.ide-settings/jetbrains/runConfigurations/Test lib no-features.run.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Test lib no-features" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="buildProfileId" value="test" />
+    <option name="command" value="test --lib --no-default-features" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="false" />
+    <option name="allFeatures" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="NO" />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.ide-settings/jetbrains/runConfigurations/Test lib no-std.run.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Test lib no-std" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="buildProfileId" value="test" />
+    <option name="command" value="test --lib --no-default-features --features &quot;colored, float&quot;" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="false" />
+    <option name="allFeatures" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="NO" />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.ide-settings/jetbrains/runConfigurations/Test lib.run.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Test lib" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="buildProfileId" value="test" />
+    <option name="command" value="test --lib --all-features" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="false" />
+    <option name="allFeatures" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="NO" />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.ide-settings/jetbrains/runConfigurations/Test no-features.run.xml

@@ -0,0 +1,20 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Test no-features" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="buildProfileId" value="test" />
+    <option name="command" value="test --no-default-features" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
+    <option name="emulateTerminal" value="false" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="false" />
+    <option name="allFeatures" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="buildTarget" value="REMOTE" />
+    <option name="backtrace" value="NO" />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

.ide-settings/jetbrains/runConfigurations/Test no-std.run.xml

@@ -1,7 +1,7 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="Test no-std" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
     <option name="buildProfileId" value="test" />
-    <option name="command" value="test --no-default-features" />
+    <option name="command" value="test --no-default-features --features &quot;colored, float&quot;" />
     <option name="workingDirectory" value="file://$PROJECT_DIR$" />
     <envs />
     <option name="emulateTerminal" value="false" />

Cargo.toml

@@ -18,7 +18,8 @@ categories = ["development-tools::testing", "no-std"]
 all-features = true
 
 [features]
-default = ["std", "panic", "float"]
+default = ["std", "colored", "float", "panic"]
+colored = ["dep:sdiff"]
 float = ["dep:float-cmp"]
 panic = ["std"]
 std = []
@@ -28,9 +29,12 @@ hashbrown = "0.15"
 
 # optional
 float-cmp = { version = "0.10", optional = true }
+sdiff = { version = "0.1", optional = true }
 
 [dev-dependencies]
 anyhow = "1"
+proptest = "1"
+serial_test = "3"
 version-sync = "0.9"
 
 [lints.rust]
@@ -55,7 +59,7 @@ unused_lifetimes = "warn"
 unused_qualifications = "warn"
 dead_code = "warn"
 missing_docs = "warn"  # uncomment when working on docs
-#variant_size_differences = "warn"  # enable when working on performance
+variant_size_differences = "warn"  # enable when working on performance
 
 [lints.clippy]
 pedantic = { level = "warn", priority = -1 }
@@ -70,5 +74,3 @@ option_if_let_else = "allow"
 print_stderr = "deny"
 print_stdout = "deny"
 unwrap_used = "deny"
-missing_errors_doc = "allow"  # remove when working on docs
-missing_panics_doc = "allow"  # remove when working on docs

README.md

@@ -73,6 +73,39 @@ asserting = { version = "0.2", default-features = false, features = "float" }
 
 An allocator is still needed for no-std.
 
+## Highlighted differences
+
+`asserting` can highlight the differences between the expected value(s) and the actual value(s) when
+printing assertion failures to the terminal. It supports different variants of how differences are
+highlighted.
+
+| Mode       | Effect                                                                                                                            |
+|------------|-----------------------------------------------------------------------------------------------------------------------------------|
+| bold       | Differences are printed in bold letters, without coloring.                                                                        | 
+| red-green  | Differences are printed in the colors <span style="color: green">green</span> and <span style="color: red">red</span>.            | 
+| red-blue   | Differences are printed in the CVD-friendly colors <span style="color: blue">blue</span> and <span style="color: red">red</span>. | 
+| red-yellow | Differences are printed in the colors <span style="color: yellow">yellow</span> and <span style="color: red">red</span>.          | 
+| off        | Switches off highlighting. The differences are not highlighted at all.                                                            | 
+
+The mode can be configured by setting the environment variable `ASSERTING_HIGHLIGHT_DIFFS` to one
+of the modes in the table above. The value is case-insensitive. E.g. setting the environment
+variable to values like `Red-Blue`, `Bold` or `OFF` works as well.
+
+The intended way for configuring the highlighting mode is to set the environment variable in the
+configuration for `Cargo` by adding it to the `[env]` section in your `~/.cargo/config.toml` file:
+
+```toml,no_sync
+[env]
+ASSERTING_HIGHLIGHT_DIFFS = "red-blue"
+```
+
+By default the mode `red-green` is used. Differences are colored in
+<span style="color: green">green</span> and <span style="color: red">red</span>.
+
+Differences are only highlighted if the crate feature `colored` is enabled. The configuration via
+the environment variable only works when the crate feature `std` is enabled too. In no-std projects
+the default colors red and green are used.
+
 ## Available Assertions
 
 This chapter gives an overview for the assertions provided by `asserting`. For a comprehensive list

justfile

@@ -29,27 +29,37 @@ check:
 lint:
     just lint-all-features
     just lint-no-std
+    just lint-no-features
 
-# linting code using Clippy --all-features
+# linting code using Clippy with all features enabled
 lint-all-features:
     cargo clippy --all-targets --all-features
 
-# linting code using Clippy - no-std
+# linting code using Clippy for no-std environment
 lint-no-std:
-    cargo clippy --all-targets --no-default-features --features "float"
+    cargo clippy --all-targets --no-default-features --features "colored, float"
+
+# linting code using Clippy with no features enabled
+lint-no-features:
+    cargo clippy --all-targets --no-default-features
 
 # run all tests
 test:
     just test-all-features
     just test-no-std
+    just test-no-features
 
 # run tests for all features
 test-all-features:
     cargo test --all-features
 
-# run tests for no-std
+# run tests for no-std environment
 test-no-std:
-    cargo test --no-default-features --features "float"
+    cargo test --no-default-features --features "colored, float"
+
+# run tests with no features enabled
+test-no-features:
+    cargo test --no-default-features
 
 # run code coverage (does not include doc-tests)
 code-coverage:

src/boolean/mod.rs

@@ -1,8 +1,9 @@
 //! Implementation of assertions for values of type `bool`.
 
 use crate::assertions::AssertBoolean;
+use crate::colored::{mark_missing, mark_unexpected};
 use crate::expectations::{IsFalse, IsTrue};
-use crate::spec::{Expectation, Expression, FailingStrategy, Spec};
+use crate::spec::{DiffFormat, Expectation, Expression, FailingStrategy, Spec};
 use crate::std::format;
 use crate::std::string::String;
 
@@ -24,10 +25,12 @@ impl Expectation<bool> for IsTrue {
         *subject
     }
 
-    fn message(&self, expression: Expression<'_>, actual: &bool) -> String {
+    fn message(&self, expression: Expression<'_>, actual: &bool, format: &DiffFormat) -> String {
+        let marked_actual = mark_unexpected(actual, format);
+        let marked_expected = mark_missing(&true, format);
         format!(
-            "expected {expression} is {:?}\n   but was: {actual:?}\n  expected: {:?}",
-            true, true
+            "expected {expression} is {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
+            true
         )
     }
 }
@@ -37,10 +40,12 @@ impl Expectation<bool> for IsFalse {
         !*subject
     }
 
-    fn message(&self, expression: Expression<'_>, actual: &bool) -> String {
+    fn message(&self, expression: Expression<'_>, actual: &bool, format: &DiffFormat) -> String {
+        let marked_actual = mark_unexpected(actual, format);
+        let marked_expected = mark_missing(&false, format);
         format!(
-            "expected {expression} is {:?}\n   but was: {actual:?}\n  expected: {:?}",
-            false, false
+            "expected {expression} is {:?}\n   but was: {marked_actual}\n  expected: {marked_expected}",
+            false
         )
     }
 }

src/boolean/tests.rs

@@ -69,3 +69,40 @@ fn verify_bool_is_false_fails() {
 "]
     );
 }
+
+#[cfg(feature = "colored")]
+mod colored {
+    use crate::prelude::*;
+
+    #[test]
+    fn highlight_diffs_bool_is_true() {
+        let failures = verify_that(37 == 42)
+            .with_diff_format(DIFF_FORMAT_RED_GREEN)
+            .is_true()
+            .display_failures();
+
+        assert_eq!(
+            failures,
+            &["assertion failed: expected subject is true\n   \
+               but was: \u{1b}[31mfalse\u{1b}[0m\n  \
+              expected: \u{1b}[32mtrue\u{1b}[0m\n\
+            "]
+        );
+    }
+
+    #[test]
+    fn highlight_diffs_bool_is_false() {
+        let failures = verify_that(42 == 42)
+            .with_diff_format(DIFF_FORMAT_RED_YELLOW)
+            .is_false()
+            .display_failures();
+
+        assert_eq!(
+            failures,
+            &["assertion failed: expected subject is false\n   \
+               but was: \u{1b}[31mtrue\u{1b}[0m\n  \
+              expected: \u{1b}[33mfalse\u{1b}[0m\n\
+            "]
+        );
+    }
+}