diff --git a/streams/transform-streams/cancel.any.js b/streams/transform-streams/cancel.any.js
new file mode 100644
index 00000000000000..5c7fc4eae5d55b
--- /dev/null
+++ b/streams/transform-streams/cancel.any.js
@@ -0,0 +1,115 @@
+// META: global=window,worker,shadowrealm
+// META: script=../resources/test-utils.js
+'use strict';
+
+const thrownError = new Error('bad things are happening!');
+thrownError.name = 'error1';
+
+const originalReason = new Error('original reason');
+originalReason.name = 'error2';
+
+promise_test(async t => {
+  let cancelled = undefined;
+  const ts = new TransformStream({
+    cancel(reason) {
+      cancelled = reason;
+    }
+  });
+  const res = await ts.readable.cancel(thrownError);
+  assert_equals(res, undefined, 'readable.cancel() should return undefined');
+  assert_equals(cancelled, thrownError, 'transformer.cancel() should be called with the passed reason');
+}, 'cancelling the readable side should call transformer.cancel()');
+
+promise_test(async t => {
+  const ts = new TransformStream({
+    cancel(reason) {
+      assert_equals(reason, originalReason, 'transformer.cancel() should be called with the passed reason');
+      throw thrownError;
+    }
+  });
+  const writer = ts.writable.getWriter();
+  const cancelPromise = ts.readable.cancel(originalReason);
+  await promise_rejects_exactly(t, thrownError, cancelPromise, 'readable.cancel() should reject with thrownError');
+  await promise_rejects_exactly(t, thrownError, writer.closed, 'writer.closed should reject with thrownError');
+}, 'cancelling the readable side should reject if transformer.cancel() throws');
+
+promise_test(async t => {
+  let aborted = undefined;
+  const ts = new TransformStream({
+    cancel(reason) {
+      aborted = reason;
+    },
+    flush: t.unreached_func('flush should not be called')
+  });
+  const res = await ts.writable.abort(thrownError);
+  assert_equals(res, undefined, 'writable.abort() should return undefined');
+  assert_equals(aborted, thrownError, 'transformer.abort() should be called with the passed reason');
+}, 'aborting the writable side should call transformer.abort()');
+
+promise_test(async t => {
+  const ts = new TransformStream({
+    cancel(reason) {
+      assert_equals(reason, originalReason, 'transformer.cancel() should be called with the passed reason');
+      throw thrownError;
+    },
+    flush: t.unreached_func('flush should not be called')
+  });
+  const reader = ts.readable.getReader();
+  const abortPromise = ts.writable.abort(originalReason);
+  await promise_rejects_exactly(t, thrownError, abortPromise, 'writable.abort() should reject with thrownError');
+  await promise_rejects_exactly(t, thrownError, reader.closed, 'reader.closed should reject with thrownError');
+}, 'aborting the writable side should reject if transformer.cancel() throws');
+
+promise_test(async t => {
+  const ts = new TransformStream({
+    async cancel(reason) {
+      assert_equals(reason, originalReason, 'transformer.cancel() should be called with the passed reason');
+      throw thrownError;
+    },
+    flush: t.unreached_func('flush should not be called')
+  });
+  const cancelPromise = ts.readable.cancel(originalReason);
+  const closePromise = ts.writable.close();
+  await Promise.all([
+    promise_rejects_exactly(t, thrownError, cancelPromise, 'cancelPromise should reject with thrownError'),
+    promise_rejects_exactly(t, thrownError, closePromise, 'closePromise should reject with thrownError'),
+  ]);
+}, 'closing the writable side should reject if a parallel transformer.cancel() throws');
+
+promise_test(async t => {
+  let controller;
+  const ts = new TransformStream({
+    start(c) {
+      controller = c;
+    },
+    async cancel(reason) {
+      assert_equals(reason, originalReason, 'transformer.cancel() should be called with the passed reason');
+      controller.error(thrownError);
+    },
+    flush: t.unreached_func('flush should not be called')
+  });
+  const cancelPromise = ts.readable.cancel(originalReason);
+  const closePromise = ts.writable.close();
+  await Promise.all([
+    promise_rejects_exactly(t, thrownError, cancelPromise, 'cancelPromise should reject with thrownError'),
+    promise_rejects_exactly(t, thrownError, closePromise, 'closePromise should reject with thrownError'),
+  ]);
+}, 'readable.cancel() and a parallel writable.close() should reject if a transformer.cancel() calls controller.error()');
+
+promise_test(async t => {
+  let controller;
+  const ts = new TransformStream({
+    start(c) {
+      controller = c;
+    },
+    async cancel(reason) {
+      assert_equals(reason, originalReason, 'transformer.cancel() should be called with the passed reason');
+      controller.error(thrownError);
+    },
+    flush: t.unreached_func('flush should not be called')
+  });
+  const cancelPromise = ts.writable.abort(originalReason);
+  await promise_rejects_exactly(t, thrownError, cancelPromise, 'cancelPromise should reject with thrownError');
+  const closePromise = ts.readable.cancel(1);
+  await promise_rejects_exactly(t, thrownError, closePromise, 'closePromise should reject with thrownError');
+}, 'writable.abort() and readable.cancel() should reject if a transformer.cancel() calls controller.error()');
diff --git a/streams/transform-streams/errors.any.js b/streams/transform-streams/errors.any.js
index 678234cc738789..bea060b6590818 100644
--- a/streams/transform-streams/errors.any.js
+++ b/streams/transform-streams/errors.any.js
@@ -9,7 +9,8 @@ promise_test(t => {
   const ts = new TransformStream({
     transform() {
       throw thrownError;
-    }
+    },
+    cancel: t.unreached_func('cancel should not be called')
   });
 
   const reader = ts.readable.getReader();
@@ -34,7 +35,8 @@ promise_test(t => {
     },
     flush() {
       throw thrownError;
-    }
+    },
+    cancel: t.unreached_func('cancel should not be called')
   });
 
   const reader = ts.readable.getReader();
@@ -54,13 +56,14 @@ promise_test(t => {
   ]);
 }, 'TransformStream errors thrown in flush put the writable and readable in an errored state');
 
-test(() => {
+test(t => {
   new TransformStream({
     start(c) {
       c.enqueue('a');
       c.error(new Error('generic error'));
       assert_throws_js(TypeError, () => c.enqueue('b'), 'enqueue() should throw');
-    }
+    },
+    cancel: t.unreached_func('cancel should not be called')
   });
 }, 'errored TransformStream should not enqueue new chunks');
 
@@ -72,7 +75,8 @@ promise_test(t => {
       });
     },
     transform: t.unreached_func('transform should not be called'),
-    flush: t.unreached_func('flush should not be called')
+    flush: t.unreached_func('flush should not be called'),
+    cancel: t.unreached_func('cancel should not be called')
   });
 
   const writer = ts.writable.getWriter();
@@ -96,7 +100,8 @@ promise_test(t => {
         });
     },
     transform: t.unreached_func('transform should never be called if start() fails'),
-    flush: t.unreached_func('flush should never be called if start() fails')
+    flush: t.unreached_func('flush should never be called if start() fails'),
+    cancel: t.unreached_func('cancel should never be called if start() fails')
   });
 
   const writer = ts.writable.getWriter();
@@ -202,9 +207,10 @@ promise_test(t => {
   return Promise.all([
     abortPromise,
     cancelPromise,
-    promise_rejects_exactly(t, thrownError, writer.closed, 'writer.closed should reject with thrownError')]);
-}, 'abort should set the close reason for the writable when it happens before cancel during start, but cancel should ' +
-             'still succeed');
+    promise_rejects_exactly(t, thrownError, writer.closed, 'writer.closed should reject'),
+  ]);
+}, 'abort should set the close reason for the writable when it happens before cancel during start, and cancel should ' +
+             'reject');
 
 promise_test(t => {
   let resolveTransform;
@@ -251,13 +257,26 @@ promise_test(t => {
       controller = c;
     }
   });
-  const cancelPromise = ts.readable.cancel(thrownError);
-  controller.error(ignoredError);
+  const cancelPromise = ts.readable.cancel(ignoredError);
+  controller.error(thrownError);
   return Promise.all([
     cancelPromise,
     promise_rejects_exactly(t, thrownError, ts.writable.getWriter().closed, 'closed should reject with thrownError')
   ]);
-}, 'controller.error() should do nothing after readable.cancel()');
+}, 'controller.error() should close writable immediately after readable.cancel()');
+
+promise_test(t => {
+  let controller;
+  const ts = new TransformStream({
+    start(c) {
+      controller = c;
+    }
+  });
+  return ts.readable.cancel(thrownError).then(() => {
+    controller.error(ignoredError);
+    return promise_rejects_exactly(t, thrownError, ts.writable.getWriter().closed, 'closed should reject with thrownError');
+  });
+}, 'controller.error() should do nothing after readable.cancel() resolves');
 
 promise_test(t => {
   let controller;
diff --git a/streams/transform-streams/flush.any.js b/streams/transform-streams/flush.any.js
index 059d8ce954e245..c95d8ae1186518 100644
--- a/streams/transform-streams/flush.any.js
+++ b/streams/transform-streams/flush.any.js
@@ -129,3 +129,18 @@ promise_test(t => {
   });
   return promise_rejects_exactly(t, error1, ts.writable.getWriter().close(), 'close() should reject');
 }, 'error() during flush should cause writer.close() to reject');
+
+promise_test(async t => {
+  let flushed = false;
+  const ts = new TransformStream({
+    flush() {
+      flushed = true;
+    },
+    cancel: t.unreached_func('cancel should not be called')
+  });
+  const closePromise = ts.writable.close();
+  await delay(0);
+  const cancelPromise = ts.readable.cancel(error1);
+  await Promise.all([closePromise, cancelPromise]);
+  assert_equals(flushed, true, 'transformer.flush() should be called');
+}, 'closing the writable side should call transformer.flush() and a parallel readable.cancel() should not reject');
diff --git a/streams/transform-streams/general.any.js b/streams/transform-streams/general.any.js
index 76bf90262a2695..a40ef30843ec4d 100644
--- a/streams/transform-streams/general.any.js
+++ b/streams/transform-streams/general.any.js
@@ -388,9 +388,24 @@ promise_test(t => {
   controller.terminate();
   return Promise.all([
     cancelPromise,
-    promise_rejects_exactly(t, cancelReason, ts.writable.getWriter().closed, 'closed should reject with cancelReason')
+    promise_rejects_js(t, TypeError, ts.writable.getWriter().closed, 'closed should reject with TypeError')
   ]);
-}, 'terminate() should do nothing after readable.cancel()');
+}, 'terminate() should abort writable immediately after readable.cancel()');
+
+promise_test(t => {
+  let controller;
+  const ts = new TransformStream({
+    start(c) {
+      controller = c;
+    }
+  });
+  const cancelReason = { name: 'cancelReason' };
+  return ts.readable.cancel(cancelReason).then(() => {
+    controller.terminate();
+    return promise_rejects_exactly(t, cancelReason, ts.writable.getWriter().closed, 'closed should reject with TypeError');
+  })
+}, 'terminate() should do nothing after readable.cancel() resolves');
+
 
 promise_test(() => {
   let calls = 0;
diff --git a/streams/transform-streams/reentrant-strategies.any.js b/streams/transform-streams/reentrant-strategies.any.js
index 15596546f70f18..a6d459655856a7 100644
--- a/streams/transform-streams/reentrant-strategies.any.js
+++ b/streams/transform-streams/reentrant-strategies.any.js
@@ -314,6 +314,10 @@ promise_test(t => {
   // call to TransformStreamDefaultSink.
   return delay(0).then(() => {
     controller.enqueue('a');
+    return reader.read();
+  }).then(({ value, done }) => {
+    assert_false(done, 'done should be false');
+    assert_equals(value, 'a', 'value should be correct');
     return Promise.all([promise_rejects_exactly(t, error1, reader.read(), 'read() should reject'), abortPromise]);
   });
 }, 'writer.abort() inside size() should work');