add test

README.md

@@ -26,6 +26,14 @@ Building from source on a Raspberry Pi installs at:
 
 On Windows see [HIDAPI Releases](https://github.com/libusb/hidapi/releases/) (I've not tested Windows).
 
+## Testing
+
+There is a basic Deno test to check the HIDAPI library defined by the `DENO_USBHIDAPI` environment variable.
+
+```sh
+deno test --unstable --allow-all src/test.ts
+```
+
 ## Resources
 
 * [libusb/hidapi](https://github.com/libusb/hidapi/) — HIDAPI library for Windows, Linux, FreeBSD and macOS.

src/test.ts

@@ -0,0 +1,33 @@
+import {
+  assertEquals,
+  assertRejects
+} from 'https://deno.land/std@0.157.0/testing/asserts.ts';
+import {hidapi} from './hidapi.ts';
+import * as utils from './utils.ts';
+
+Deno.test('HIDAPI missing', () => {
+  assertRejects(
+    () =>
+      new Promise((resolve, reject) => {
+        Deno.env.set('DENO_USBHIDAPI', './missing');
+        import('./hidapi.ts?nocache').then(resolve).catch(reject);
+      })
+  );
+});
+
+Deno.test('HIDAPI version number', () => {
+  const buffer = Deno.UnsafePointerView.getArrayBuffer(
+    hidapi.symbols.hid_version(),
+    24
+  );
+  const view = new DataView(buffer);
+  assertEquals(view.getUint8(4), 12);
+});
+
+Deno.test('HIDAPI version string ("0.12.0")', () => {
+  const buffer = Deno.UnsafePointerView.getArrayBuffer(
+    hidapi.symbols.hid_version_str(),
+    32
+  );
+  assertEquals(utils.decodeUTF8(buffer), '0.12.0');
+});