feat: Add feature for testing colored output easier

Author: Muscraft

Diff for: Cargo.toml

@@ -40,3 +40,4 @@ harness = false
 
 [features]
 default = []
+testing-colors = []

Diff for: src/lib.rs

@@ -40,6 +40,15 @@
 //! options, such as color, or margins.
 //!
 //! Finally, `impl Display` into a final `String` output.
+//!
+//! # features
+//! - `testing-colors` - Makes [Renderer::styled] colors OS independent, which
+//! allows for easier testing when testing colored output. It should be added as
+//! a feature in `[dev-dependencies]`, which can be done with the following command:
+//! ```text
+//! cargo add annotate-snippets --dev --feature testing-colors
+//! ```
+//!
 
 pub mod renderer;
 mod snippet;

Diff for: src/renderer/mod.rs

@@ -61,16 +61,25 @@ impl Renderer {
     }
 
     /// Default terminal styling
+    ///
+    /// # Note
+    /// Some colors are OS dependant, meaning that the colors will look
+    /// different on different operating systems, making testing colored output
+    /// difficult.
+    /// If you are testing the colored output, you can use the
+    /// [`testing-colors` feature](crate#features) to enable colors that are OS
+    /// independent.
     pub const fn styled() -> Self {
-        const BRIGHT_BLUE: Style = if cfg!(windows) {
+        const USE_WINDOWS_COLORS: bool = cfg!(windows) && !cfg!(feature = "testing-colors");
+        const BRIGHT_BLUE: Style = if USE_WINDOWS_COLORS {
             AnsiColor::BrightCyan.on_default()
         } else {
             AnsiColor::BrightBlue.on_default()
         };
         Self {
             stylesheet: Stylesheet {
                 error: AnsiColor::BrightRed.on_default().effects(Effects::BOLD),
-                warning: if cfg!(windows) {
+                warning: if USE_WINDOWS_COLORS {
                     AnsiColor::BrightYellow.on_default()
                 } else {
                     AnsiColor::Yellow.on_default()
@@ -80,7 +89,7 @@ impl Renderer {
                 note: AnsiColor::BrightGreen.on_default().effects(Effects::BOLD),
                 help: AnsiColor::BrightCyan.on_default().effects(Effects::BOLD),
                 line_no: BRIGHT_BLUE.effects(Effects::BOLD),
-                emphasis: if cfg!(windows) {
+                emphasis: if USE_WINDOWS_COLORS {
                     AnsiColor::BrightWhite.on_default()
                 } else {
                     Style::new()