diff --git a/test/__fixtures__/plugin-extensions/file.foo b/test/__fixtures__/plugin-extensions/file.foo
new file mode 100644
index 0000000..12f00e9
--- /dev/null
+++ b/test/__fixtures__/plugin-extensions/file.foo
@@ -0,0 +1 @@
+contents
diff --git a/test/__fixtures__/plugin-extensions/plugin.cjs b/test/__fixtures__/plugin-extensions/plugin.cjs
new file mode 100644
index 0000000..be9f6c9
--- /dev/null
+++ b/test/__fixtures__/plugin-extensions/plugin.cjs
@@ -0,0 +1,24 @@
+"use strict";
+
+module.exports = {
+  languages: [
+    {
+      name: "foo",
+      parsers: ["foo-parser"],
+      extensions: [".foo"],
+    },
+  ],
+  parsers: {
+    "foo-parser": {
+      parse: (text) => ({ text }),
+      astFormat: "foo-ast",
+    },
+  },
+  printers: {
+    "foo-ast": {
+      print(path) {
+        return ["!", path.getValue().text];
+      },
+    },
+  },
+};
diff --git a/test/__tests__/plugin-extensions.js b/test/__tests__/plugin-extensions.js
new file mode 100644
index 0000000..cbfcbbd
--- /dev/null
+++ b/test/__tests__/plugin-extensions.js
@@ -0,0 +1,15 @@
+import { runCli } from "../utils";
+
+describe("uses 'extensions' from languages to determine parser", () => {
+  runCli("plugin-extensions", [
+    "*.foo",
+    "--plugin=./plugin.cjs",
+  ], {
+    ignoreLineEndings: true,
+  }).test({
+    stdout: "!contents",
+    stderr: "",
+    status: 0,
+    write: [],
+  });
+});
diff --git a/test/__tests__/plugin-flush-line-suffix.js b/test/__tests__/plugin-flush-line-suffix.js
index 7e9bc9d..bd25b09 100644
--- a/test/__tests__/plugin-flush-line-suffix.js
+++ b/test/__tests__/plugin-flush-line-suffix.js
@@ -3,7 +3,7 @@ import { runCli } from "../utils";
 describe("flush all line-suffix content", () => {
   runCli("plugin-flush-line-suffix", [
     "*.foo",
-    "--plugin=./plugin.cjs"
+    "--plugin=./plugin.cjs",
   ], {
     ignoreLineEndings: true,
   }).test({