1 files changed, 71 insertions, 0 deletions
diff --git a/preact/hooks/test/browser/useDebugValue.test.js b/preact/hooks/test/browser/useDebugValue.test.js
new file mode 100644
index 0000000..d19ff6b
--- /dev/null
+++ b/preact/hooks/test/browser/useDebugValue.test.js
@@ -0,0 +1,71 @@
+import { createElement, render, options } from 'preact';
+import { setupScratch, teardown } from '../../../test/_util/helpers';
+import { useDebugValue, useState } from 'preact/hooks';
+
+/** @jsx createElement */
+
+describe('useDebugValue', () => {
+	/** @type {HTMLDivElement} */
+	let scratch;
+
+	beforeEach(() => {
+		scratch = setupScratch();
+	});
+
+	afterEach(() => {
+		teardown(scratch);
+		delete options.useDebugValue;
+	});
+
+	it('should do nothing when no options hook is present', () => {
+		function useFoo() {
+			useDebugValue('foo');
+			return useState(0);
+		}
+
+		function App() {
+			let [v] = useFoo();
+			return <div>{v}</div>;
+		}
+
+		expect(() => render(<App />, scratch)).to.not.throw();
+	});
+
+	it('should call options hook with value', () => {
+		let spy = (options.useDebugValue = sinon.spy());
+
+		function useFoo() {
+			useDebugValue('foo');
+			return useState(0);
+		}
+
+		function App() {
+			let [v] = useFoo();
+			return <div>{v}</div>;
+		}
+
+		render(<App />, scratch);
+
+		expect(spy).to.be.calledOnce;
+		expect(spy).to.be.calledWith('foo');
+	});
+
+	it('should apply optional formatter', () => {
+		let spy = (options.useDebugValue = sinon.spy());
+
+		function useFoo() {
+			useDebugValue('foo', x => x + 'bar');
+			return useState(0);
+		}
+
+		function App() {
+			let [v] = useFoo();
+			return <div>{v}</div>;
+		}
+
+		render(<App />, scratch);
+
+		expect(spy).to.be.calledOnce;
+		expect(spy).to.be.calledWith('foobar');
+	});
+});