chore: use the fakeenv crate for testing environment variable specific functionality

Cargo.toml

@@ -43,8 +43,8 @@ sdiff = { version = "0.1", optional = true }
 
 [dev-dependencies]
 anyhow = "1"
+fakeenv = { version = "0.1", default-features = false, features = ["fake"] }
 proptest = "1"
-serial_test = "3"
 time = { version = "0.3", default-features = false, features = ["macros"] }
 version-sync = "0.9"
 

examples/fixture/mod.rs

@@ -4,6 +4,7 @@ mod dummy_extern_uses {
     use anyhow as _;
     #[cfg(feature = "bigdecimal")]
     use bigdecimal as _;
+    use fakeenv as _;
     #[cfg(feature = "float-cmp")]
     use float_cmp as _;
     use hashbrown as _;
@@ -18,7 +19,6 @@ mod dummy_extern_uses {
     use rust_decimal as _;
     #[cfg(feature = "colored")]
     use sdiff as _;
-    use serial_test as _;
     use time as _;
     use version_sync as _;
 }

src/colored/mod.rs

@@ -699,7 +699,7 @@ mod with_colored_feature {
     /// Returns true if the environment variable `NO_COLOR` is set.
     #[cfg(feature = "std")]
     fn is_no_color_env_var_set() -> bool {
-        use crate::std::env;
+        use crate::env;
 
         match env::var(ENV_VAR_NO_COLOR) {
             Ok(value) => !value.is_empty(),
@@ -718,7 +718,7 @@ mod with_colored_feature {
     #[must_use]
     #[inline]
     pub fn configured_diff_format_impl() -> DiffFormat {
-        use crate::std::env;
+        use crate::env;
 
         match env::var(ENV_VAR_HIGHLIGHT_DIFFS) {
             Ok(value) => {

src/colored/tests.rs

@@ -90,13 +90,11 @@ mod with_colored_but_not_std_feature {
 mod with_colored_and_std_features {
     use super::*;
     use crate::colored::with_colored_feature::ENV_VAR_HIGHLIGHT_DIFFS;
-    use crate::std::env;
+    use crate::env;
     use hashbrown::HashMap;
     use proptest::prelude::*;
-    use serial_test::serial;
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_not_set() {
         env::remove_var(ENV_VAR_HIGHLIGHT_DIFFS);
 
@@ -106,7 +104,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_not_set_and_no_color_env_var_set() {
         env::remove_var(ENV_VAR_HIGHLIGHT_DIFFS);
         env::set_var("NO_COLOR", "1");
@@ -119,7 +116,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_unknown_mode() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "not-valid");
 
@@ -129,7 +125,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_bold_mode() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "bold");
 
@@ -139,7 +134,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_bold_mode_and_no_color_env_var_set() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "bold");
         env::set_var("NO_COLOR", "1");
@@ -152,7 +146,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_green_mode() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-green");
 
@@ -162,7 +155,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_green_mode_and_no_color_env_var_set() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-green");
         env::set_var("NO_COLOR", "1");
@@ -175,7 +167,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_blue_mode() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-blue");
 
@@ -185,7 +176,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_blue_mode_and_no_color_env_var_set() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-blue");
         env::set_var("NO_COLOR", "1");
@@ -198,7 +188,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_yellow_mode() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-yellow");
 
@@ -208,7 +197,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_red_yellow_mode_and_no_color_env_var_set() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-yellow");
         env::set_var("NO_COLOR", "1");
@@ -221,7 +209,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn get_configured_diff_format_when_env_var_set_to_off() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "off");
 
@@ -232,47 +219,43 @@ mod with_colored_and_std_features {
 
     proptest! {
         #[test]
-        #[serial]
         fn setting_env_var_to_bold_is_case_insensitive(
             mode in "[bB][oO][lL][dD]"
         ) {
-            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, mode);
+            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, &mode);
 
             let diff_format = configured_diff_format();
 
             prop_assert_eq!(diff_format, DIFF_FORMAT_BOLD);
         }
 
         #[test]
-        #[serial]
         fn setting_env_var_to_red_blue_is_case_insensitive(
             mode in "[rR][eE][dD]-[bB][lL][uU][eE]"
         ) {
-            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, mode);
+            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, &mode);
 
             let diff_format = configured_diff_format();
 
             prop_assert_eq!(diff_format, DIFF_FORMAT_RED_BLUE);
         }
 
         #[test]
-        #[serial]
         fn setting_env_var_to_red_yellow_is_case_insensitive(
             mode in "[rR][eE][dD]-[yY][eE][lL][lL][oO][wW]"
         ) {
-            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, mode);
+            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, &mode);
 
             let diff_format = configured_diff_format();
 
             prop_assert_eq!(diff_format, DIFF_FORMAT_RED_YELLOW);
         }
 
         #[test]
-        #[serial]
         fn setting_env_var_to_off_is_case_insensitive(
             mode in "[oO][fF][fF]"
         ) {
-            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, mode);
+            env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, &mode);
 
             let diff_format = configured_diff_format();
 
@@ -281,7 +264,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn assert_that_sets_the_diff_format_to_red_green() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-green");
 
@@ -291,7 +273,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn verify_that_sets_the_diff_format_to_no_highlighting() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-green");
 
@@ -301,7 +282,6 @@ mod with_colored_and_std_features {
     }
 
     #[test]
-    #[serial]
     fn assert_that_code_sets_the_diff_format_to_red_green() {
         env::set_var(ENV_VAR_HIGHLIGHT_DIFFS, "red-green");
 

src/env.rs

@@ -0,0 +1,36 @@
+//! Fakeable `env` module for tests.
+//!
+//! inspired by
+//! [Testing code that uses environment variables](https://www.reddit.com/r/rust/comments/1jd8sxg/testing_code_that_uses_environment_variables/)
+//! - post on Reddit
+
+pub use std::env::VarError;
+
+#[cfg(not(test))]
+pub use std::env::var;
+
+#[cfg(test)]
+pub use fake_env::*;
+
+#[cfg(test)]
+mod fake_env {
+    use fakeenv::EnvStore;
+    use std::cell::RefCell;
+    use std::env::VarError;
+
+    thread_local! {
+        static ENV_STORE: RefCell<EnvStore> = RefCell::new(EnvStore::fake());
+    }
+
+    pub fn var(key: &str) -> Result<String, VarError> {
+        ENV_STORE.with(|env| env.borrow().var(key))
+    }
+
+    pub fn set_var(key: &str, value: &str) {
+        ENV_STORE.with(|env| env.borrow_mut().set_var(key, value));
+    }
+
+    pub fn remove_var(key: &str) {
+        ENV_STORE.with(|env| env.borrow_mut().remove_var(key));
+    }
+}

src/lib.rs

@@ -678,6 +678,8 @@ mod c_string;
 mod char;
 mod char_count;
 mod collection;
+#[cfg(feature = "std")]
+mod env;
 mod equality;
 mod error;
 mod float;
@@ -713,8 +715,8 @@ type TestCodeSnippetsInReadme = ();
 // Rust issue [#95513](https://github.com/rust-lang/rust/issues/95513) is fixed
 #[cfg(test)]
 mod dummy_extern_uses {
+    use fakeenv as _;
     use proptest as _;
-    use serial_test as _;
     use time as _;
     use version_sync as _;
 }

tests/version_numbers.rs

@@ -8,6 +8,7 @@ mod dummy_extern_uses {
     use asserting as _;
     #[cfg(feature = "bigdecimal")]
     use bigdecimal as _;
+    use fakeenv as _;
     #[cfg(feature = "float-cmp")]
     use float_cmp as _;
     use hashbrown as _;
@@ -22,7 +23,6 @@ mod dummy_extern_uses {
     use rust_decimal as _;
     #[cfg(feature = "colored")]
     use sdiff as _;
-    use serial_test as _;
     use time as _;
 }