diff --git a/tests/files/ignore.invalid.extension b/tests/files/ignore.invalid.extension
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/src/core/ignore.js b/tests/src/core/ignore.js
new file mode 100644
index 000000000..cc89f8454
--- /dev/null
+++ b/tests/src/core/ignore.js
@@ -0,0 +1,58 @@
+import { expect } from 'chai'
+
+import isIgnored, { hasValidExtension } from 'eslint-module-utils/ignore'
+
+import * as utils from '../utils'
+
+describe('ignore', function () {
+  describe('isIgnored', function () {
+    it('ignores paths with extensions other than .js', function () {
+      const testContext = utils.testContext({})
+
+      expect(isIgnored('../files/foo.js', testContext)).to.equal(false)
+
+      expect(isIgnored('../files/bar.jsx', testContext)).to.equal(true)
+
+      expect(isIgnored('../files/typescript.ts', testContext)).to.equal(true)
+
+      expect(isIgnored('../files/ignore.invalid.extension', testContext)).to.equal(true)
+    })
+
+    it('ignores paths with invalid extensions when configured with import/extensions', function () {
+      const testContext = utils.testContext({ 'import/extensions': [ '.js', '.jsx', '.ts' ] })
+
+      expect(isIgnored('../files/foo.js', testContext)).to.equal(false)
+
+      expect(isIgnored('../files/bar.jsx', testContext)).to.equal(false)
+
+      expect(isIgnored('../files/typescript.ts', testContext)).to.equal(false)
+
+      expect(isIgnored('../files/ignore.invalid.extension', testContext)).to.equal(true)
+    })
+  })
+
+  describe('hasValidExtension', function () {
+    it('assumes only .js as valid by default', function () {
+      const testContext = utils.testContext({})
+
+      expect(hasValidExtension('../files/foo.js', testContext)).to.equal(true)
+
+      expect(hasValidExtension('../files/foo.jsx', testContext)).to.equal(false)
+
+      expect(hasValidExtension('../files/foo.css', testContext)).to.equal(false)
+
+      expect(hasValidExtension('../files/foo.invalid.extension', testContext)).to.equal(false)
+    })
+
+    it('can be configured with import/extensions', function () {
+      const testContext = utils.testContext({ 'import/extensions': [ '.foo', '.bar' ] })
+
+      expect(hasValidExtension('../files/foo.foo', testContext)).to.equal(true)
+
+      expect(hasValidExtension('../files/foo.bar', testContext)).to.equal(true)
+
+      expect(hasValidExtension('../files/foo.js', testContext)).to.equal(false)
+    })
+  })
+
+})
diff --git a/tests/src/utils.js b/tests/src/utils.js
index 144ae5498..7a13ed432 100644
--- a/tests/src/utils.js
+++ b/tests/src/utils.js
@@ -87,4 +87,10 @@ export const SYNTAX_CASES = [
   test({
     code: 'import * as a from "./commonjs-namespace/a"; a.b',
   }),
- ]
+
+  // ignore invalid extensions
+  test({
+    code: 'import { foo } from "./ignore.invalid.extension"',
+  }),
+
+]