1 files changed, 85 insertions, 0 deletions
diff --git a/toolkit/components/nimbus/test/browser/browser_prefs.js b/toolkit/components/nimbus/test/browser/browser_prefs.js
new file mode 100644
index 0000000000..7e63618a24
--- /dev/null
+++ b/toolkit/components/nimbus/test/browser/browser_prefs.js
@@ -0,0 +1,85 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { ExperimentAPI, NimbusFeatures } = ChromeUtils.import(
+  "resource://nimbus/ExperimentAPI.jsm"
+);
+const { ExperimentFakes } = ChromeUtils.import(
+  "resource://testing-common/NimbusTestUtils.jsm"
+);
+const { ExperimentManager } = ChromeUtils.import(
+  "resource://nimbus/lib/ExperimentManager.jsm"
+);
+
+const EXPERIMENT_VALUE = "experiment-value";
+const ROLLOUT_VALUE = "rollout-value";
+const ROLLOUT = "rollout";
+const EXPERIMENT = "experiment";
+
+const VALUES = {
+  [ROLLOUT]: ROLLOUT_VALUE,
+  [EXPERIMENT]: EXPERIMENT_VALUE,
+};
+
+add_task(async function test_prefs_priority() {
+  const pref = "nimbus.testing.testSetString";
+  const featureId = "testFeature";
+
+  async function doTest({ settingEnrollments, expectedValue }) {
+    info(
+      `Enrolling in a rollout and experiment where the ${settingEnrollments.join(
+        " and "
+      )} set the same pref variable.`
+    );
+    const enrollmentCleanup = [];
+
+    for (const enrollmentKind of [ROLLOUT, EXPERIMENT]) {
+      const config = {
+        featureId,
+        value: {},
+      };
+
+      if (settingEnrollments.includes(enrollmentKind)) {
+        config.value.testSetString = VALUES[enrollmentKind];
+      }
+
+      enrollmentCleanup.push(
+        await ExperimentFakes.enrollWithFeatureConfig(config, {
+          isRollout: enrollmentKind === ROLLOUT,
+        })
+      );
+    }
+
+    is(
+      NimbusFeatures[featureId].getVariable("testSetString"),
+      expectedValue,
+      "Expected the variable to match the expected value"
+    );
+
+    is(
+      Services.prefs.getStringPref(pref),
+      expectedValue,
+      "Expected the pref to match the expected value"
+    );
+
+    for (const cleanup of enrollmentCleanup) {
+      await cleanup();
+    }
+
+    Services.prefs.deleteBranch(pref);
+  }
+
+  for (const settingEnrollments of [
+    [ROLLOUT],
+    [EXPERIMENT],
+    [ROLLOUT, EXPERIMENT],
+  ]) {
+    const expectedValue = settingEnrollments.includes(EXPERIMENT)
+      ? EXPERIMENT_VALUE
+      : ROLLOUT_VALUE;
+
+    await doTest({ settingEnrollments, expectedValue });
+  }
+});