1 files changed, 147 insertions, 0 deletions
diff --git a/devtools/client/memory/test/xpcshell/test_action_diffing_03.js b/devtools/client/memory/test/xpcshell/test_action_diffing_03.js
new file mode 100644
index 0000000000..8db0e8568b
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+++ b/devtools/client/memory/test/xpcshell/test_action_diffing_03.js
@@ -0,0 +1,147 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test selecting snapshots for diffing.
+
+const {
+  diffingState,
+  snapshotState,
+  viewState,
+} = require("resource://devtools/client/memory/constants.js");
+const {
+  toggleDiffing,
+  selectSnapshotForDiffing,
+} = require("resource://devtools/client/memory/actions/diffing.js");
+const {
+  takeSnapshot,
+} = require("resource://devtools/client/memory/actions/snapshot.js");
+const {
+  changeView,
+} = require("resource://devtools/client/memory/actions/view.js");
+
+// We test that you (1) cannot select a snapshot that is not in a diffable
+// state, and (2) cannot select more than 2 snapshots for diffing. Both attempts
+// trigger assertion failures.
+EXPECTED_DTU_ASSERT_FAILURE_COUNT = 2;
+
+add_task(async function () {
+  const front = new StubbedMemoryFront();
+  const heapWorker = new HeapAnalysesClient();
+  await front.attach();
+  const store = Store();
+  const { getState, dispatch } = store;
+
+  dispatch(changeView(viewState.CENSUS));
+  equal(getState().diffing, null, "not diffing by default");
+
+  dispatch(takeSnapshot(front, heapWorker));
+  dispatch(takeSnapshot(front, heapWorker));
+  dispatch(takeSnapshot(front, heapWorker));
+
+  await waitUntilSnapshotState(store, [
+    snapshotState.SAVED,
+    snapshotState.SAVED,
+    snapshotState.SAVED,
+  ]);
+  dispatch(takeSnapshot(front));
+
+  // Start diffing.
+  dispatch(toggleDiffing());
+  ok(getState().diffing, "now diffing after toggling");
+  equal(getState().diffing.firstSnapshotId, null, "no first snapshot selected");
+  equal(
+    getState().diffing.secondSnapshotId,
+    null,
+    "no second snapshot selected"
+  );
+  equal(
+    getState().diffing.state,
+    diffingState.SELECTING,
+    "should be in diffing state SELECTING"
+  );
+
+  // Can't select a snapshot that is not in a diffable state.
+  equal(
+    getState().snapshots[3].state,
+    snapshotState.SAVING,
+    "the last snapshot is still in the process of being saved"
+  );
+  dumpn("Expecting exception:");
+  let threw = false;
+  try {
+    dispatch(selectSnapshotForDiffing(getState().snapshots[3]));
+  } catch (error) {
+    threw = true;
+  }
+  ok(
+    threw,
+    "Should not be able to select snapshots that aren't ready for diffing"
+  );
+
+  // Select first snapshot for diffing.
+  dispatch(selectSnapshotForDiffing(getState().snapshots[0]));
+  ok(getState().diffing, "now diffing after toggling");
+  equal(
+    getState().diffing.firstSnapshotId,
+    getState().snapshots[0].id,
+    "first snapshot selected"
+  );
+  equal(
+    getState().diffing.secondSnapshotId,
+    null,
+    "no second snapshot selected"
+  );
+  equal(
+    getState().diffing.state,
+    diffingState.SELECTING,
+    "should still be in diffing state SELECTING"
+  );
+
+  // Can't diff first snapshot with itself; this is a noop.
+  dispatch(selectSnapshotForDiffing(getState().snapshots[0]));
+  ok(getState().diffing, "still diffing");
+  equal(
+    getState().diffing.firstSnapshotId,
+    getState().snapshots[0].id,
+    "first snapshot still selected"
+  );
+  equal(
+    getState().diffing.secondSnapshotId,
+    null,
+    "still no second snapshot selected"
+  );
+  equal(
+    getState().diffing.state,
+    diffingState.SELECTING,
+    "should still be in diffing state SELECTING"
+  );
+
+  // Select second snapshot for diffing.
+  dispatch(selectSnapshotForDiffing(getState().snapshots[1]));
+  ok(getState().diffing, "still diffing");
+  equal(
+    getState().diffing.firstSnapshotId,
+    getState().snapshots[0].id,
+    "first snapshot still selected"
+  );
+  equal(
+    getState().diffing.secondSnapshotId,
+    getState().snapshots[1].id,
+    "second snapshot selected"
+  );
+
+  // Can't select more than two snapshots for diffing.
+  dumpn("Expecting exception:");
+  threw = false;
+  try {
+    dispatch(selectSnapshotForDiffing(getState().snapshots[2]));
+  } catch (error) {
+    threw = true;
+  }
+  ok(threw, "Can't select more than two snapshots for diffing");
+
+  heapWorker.destroy();
+  await front.detach();
+});