test: add one more test from WPT

Author: ChALkeR

tests/wpt/fallback.test.cjs

@@ -64,6 +64,7 @@ fs.readFileSync(path.join(__dirname, 'fixtures/encoding/encodeInto.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/iso-2022-jp-decoder.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/legacy-mb-schinese/gb18030/gb18030-decoder.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/legacy-mb-schinese/gbk/gbk-decoder.any.js'))
+fs.readFileSync(path.join(__dirname, 'fixtures/encoding/streams/backpressure.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/streams/decode-attributes.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/streams/decode-bad-chunks.any.js'))
 fs.readFileSync(path.join(__dirname, 'fixtures/encoding/streams/decode-ignore-bom.any.js'))

tests/wpt/fixtures/encoding/streams/backpressure.any.js

@@ -0,0 +1,60 @@
+// META: global=window,worker,shadowrealm
+
+'use strict';
+
+const classes = [
+  {
+    name: 'TextDecoderStream',
+    input: new Uint8Array([65])
+  },
+  {
+    name: 'TextEncoderStream',
+    input: 'A'
+  }
+];
+
+const microtasksRun = () => new Promise(resolve => step_timeout(resolve, 0));
+
+for (const streamClass of classes) {
+  promise_test(async () => {
+    const stream = new self[streamClass.name]();
+    const writer = stream.writable.getWriter();
+    const reader = stream.readable.getReader();
+    const events = [];
+    await microtasksRun();
+    const writePromise = writer.write(streamClass.input);
+    writePromise.then(() => events.push('write'));
+    await microtasksRun();
+    events.push('paused');
+    await reader.read();
+    events.push('read');
+    await writePromise;
+    assert_array_equals(events, ['paused', 'read', 'write'],
+                        'write should happen after read');
+  }, 'write() should not complete until read relieves backpressure for ' +
+     `${streamClass.name}`);
+
+  promise_test(async () => {
+    const stream = new self[streamClass.name]();
+    const writer = stream.writable.getWriter();
+    const reader = stream.readable.getReader();
+    const events = [];
+    await microtasksRun();
+    const readPromise1 = reader.read();
+    readPromise1.then(() => events.push('read1'));
+    const writePromise1 = writer.write(streamClass.input);
+    const writePromise2 = writer.write(streamClass.input);
+    writePromise1.then(() => events.push('write1'));
+    writePromise2.then(() => events.push('write2'));
+    await microtasksRun();
+    events.push('paused');
+    const readPromise2 = reader.read();
+    readPromise2.then(() => events.push('read2'));
+    await Promise.all([writePromise1, writePromise2,
+                       readPromise1, readPromise2]);
+    assert_array_equals(events, ['read1', 'write1', 'paused', 'read2',
+                                 'write2'],
+                        'writes should not happen before read2');
+  }, 'additional writes should wait for backpressure to be relieved for ' +
+     `class ${streamClass.name}`);
+}

tests/wpt/loader.cjs

@@ -28,8 +28,9 @@ globalThis.generate_tests = (t, l) => {
   })
 }
 
-globalThis.assert_equals = assert.strictEqual
 globalThis.format_value = (x) => JSON.stringify(x)
+globalThis.step_timeout = setTimeout
+globalThis.assert_equals = assert.strictEqual
 globalThis.assert_true = (x, ...r) => assert.strictEqual(x, true, ...r)
 globalThis.assert_false = (x, ...r) => assert.strictEqual(x, false, ...r)
 globalThis.assert_not_equals = (a, b, ...r) => assert.notEqual(a, b, ...r)