1 files changed, 35 insertions, 0 deletions
diff --git a/tests/no_duplicate_extensions.rs b/tests/no_duplicate_extensions.rs
new file mode 100644
index 00000000..ef9e76a9
--- /dev/null
+++ b/tests/no_duplicate_extensions.rs
@@ -0,0 +1,35 @@
+use std::collections::HashSet;
+
+use bat::assets::HighlightingAssets;
+
+#[test]
+fn no_duplicate_extensions() {
+    const KNOWN_EXCEPTIONS: &[&'static str] = &[
+        // The '.h' extension currently appears in multiple syntaxes: C, C++, Objective C,
+        // Objective C++
+        "h",
+        // In addition to the standard Haskell syntax in 'Packages', we also ship the 'Cabal'
+        // syntax which comes with a "Haskell (improved)" syntax.
+        "hs",
+        // In addition to the standard JavaScript syntax in 'Packages', we also ship the
+        // 'Javascript (Babel)' syntax.
+        "js",
+        // The "Ruby Haml" syntax also comes with a '.sass' extension. However, we make sure
+        // that 'sass' is mapped to the 'Sass' syntax.
+        "sass",
+    ];
+
+    let assets = HighlightingAssets::new();
+
+    let mut extensions = HashSet::new();
+
+    for syntax in assets.syntax_set.syntaxes() {
+        for extension in &syntax.file_extensions {
+            assert!(
+                KNOWN_EXCEPTIONS.contains(&extension.as_str()) || extensions.insert(extension),
+                "File extension / pattern \"{}\" appears twice in the syntax set",
+                extension
+            );
+        }
+    }
+}