add some basic tests

package.json

@@ -31,6 +31,8 @@
 	"scripts": {
 		"build": "rollup -c",
 		"dev": "rollup -cw",
-		"prepare": "npm run build"
+		"prepare": "npm run build",
+		"pretest": "npm run build",
+		"test": "node test.js"
 	}
 }

test.js

@@ -0,0 +1,65 @@
+const assert = require('assert');
+const fs = require('fs');
+const { autocache } = require('.');
+
+let count = 0;
+const func = async () => {
+	count++;
+	return {};
+};
+
+(async () => {
+	await fs.promises.unlink('cache.test').catch(() => {});
+
+	{
+		// set value 1 and value 2 in mode 1
+		const { cache, close } = autocache('cache.test', 'm1');
+		assert.strictEqual(count, 0);
+		const v1a = await cache('v1', func);
+		assert.strictEqual(count, 1);
+		const v1b = await cache('v1', func);
+		assert.strictEqual(count, 1);
+		assert.strictEqual(v1a, v1b);
+		const v2 = await cache('v2', func);
+		assert.strictEqual(count, 2);
+		assert.notStrictEqual(v1a, v2);
+		close();
+	}
+
+	{
+		// open and close mode 2 - should not wipe values saved in mode 1
+		const { cache, close } = autocache('cache.test', 'm2');
+		close();
+	}
+
+	{
+		// check value 2 already exists in mode 2 (from mode 1)
+		const { cache, close } = autocache('cache.test', 'm2');
+		assert.strictEqual(count, 2);
+		const v2 = await cache('v2', func);
+		assert.strictEqual(count, 2);
+		close();
+	}
+
+	{
+		// check two parallel calls to value 3 (in mode 1) return the same value
+		// also clears value 1, which only exists in mode 1
+		const { cache, close } = autocache('cache.test', 'm1');
+		const [v3a, v3b] = await Promise.all([cache('v3', func), cache('v3', func)]);
+		assert.strictEqual(v3a, v3b);
+		close();
+	}
+
+	{
+		// check that value 1 no longer exists, but value 2 still does
+		const { cache, close } = autocache('cache.test', 'm2');
+		assert.strictEqual(count, 3);
+		const v1 = await cache('v1', func);
+		assert.strictEqual(count, 4);
+		const v2 = await cache('v2', func);
+		assert.strictEqual(count, 4);
+		close();
+	}
+
+	await fs.promises.unlink('cache.test').catch(() => {});
+})();