From fab4c1a216474cd5fa347e6e5e885710410e0d72 Mon Sep 17 00:00:00 2001
From: Joseph Baylon <joseph.baylon@mattermost.com>
Date: Thu, 1 Sep 2022 07:56:31 -0700
Subject: [PATCH] Detox/E2E: Add custom test sequencer (#6611)

* Detox/E2E: Add custom test sequencer

* Fix lint

* Added explicit dev dependency on sequencer
---
 detox/e2e/config.js           |  1 +
 detox/e2e/custom_sequencer.js | 31 +++++++++++++++++++++++++++++++
 detox/package-lock.json       |  1 +
 detox/package.json            |  1 +
 4 files changed, 34 insertions(+)
 create mode 100644 detox/e2e/custom_sequencer.js

diff --git a/detox/e2e/config.js b/detox/e2e/config.js
index bfb89b83d..b8d09a885 100644
--- a/detox/e2e/config.js
+++ b/detox/e2e/config.js
@@ -8,6 +8,7 @@ module.exports = {
     maxWorkers: 1,
     testEnvironment: './environment',
     testRunner: 'jest-circus/runner',
+    testSequencer: './custom_sequencer.js',
     testTimeout: 120000,
     testRegex: '\\.e2e\\.ts$',
     transform: {
diff --git a/detox/e2e/custom_sequencer.js b/detox/e2e/custom_sequencer.js
new file mode 100644
index 000000000..827166cb2
--- /dev/null
+++ b/detox/e2e/custom_sequencer.js
@@ -0,0 +1,31 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+const Sequencer = require('@jest/test-sequencer').default;
+
+class CustomSequencer extends Sequencer {
+    /**
+     * Select tests for shard requested via --shard=shardIndex/shardCount
+     * Sharding is applied before sorting
+     */
+    shard(tests, {shardIndex, shardCount}) {
+        const shardSize = Math.ceil(tests.length / shardCount);
+        const shardStart = shardSize * (shardIndex - 1);
+        const shardEnd = shardSize * shardIndex;
+
+        return [...tests].sort((a, b) => (a.path > b.path ? 1 : -1)).slice(shardStart, shardEnd);
+    }
+
+    /**
+     * Sort test to determine order of execution
+     * Sorting is applied after sharding
+     */
+    sort(tests) {
+        // Test structure information
+        // https://github.com/facebook/jest/blob/6b8b1404a1d9254e7d5d90a8934087a9c9899dab/packages/jest-runner/src/types.ts#L17-L21
+        const copyTests = Array.from(tests);
+        return copyTests.sort((testA, testB) => (testA.path > testB.path ? 1 : -1));
+    }
+}
+
+module.exports = CustomSequencer;
diff --git a/detox/package-lock.json b/detox/package-lock.json
index 2fbd47bd6..af39188ae 100644
--- a/detox/package-lock.json
+++ b/detox/package-lock.json
@@ -10,6 +10,7 @@
         "@babel/plugin-transform-modules-commonjs": "7.18.6",
         "@babel/plugin-transform-runtime": "7.18.10",
         "@babel/preset-env": "7.18.10",
+        "@jest/test-sequencer": "28.1.3",
         "@types/jest": "28.1.6",
         "@types/tough-cookie": "4.0.2",
         "@types/uuid": "8.3.4",
diff --git a/detox/package.json b/detox/package.json
index 9e81ee512..6e53f2569 100644
--- a/detox/package.json
+++ b/detox/package.json
@@ -8,6 +8,7 @@
     "@babel/plugin-transform-modules-commonjs": "7.18.6",
     "@babel/plugin-transform-runtime": "7.18.10",
     "@babel/preset-env": "7.18.10",
+    "@jest/test-sequencer": "28.1.3",
     "@types/jest": "28.1.6",
     "@types/tough-cookie": "4.0.2",
     "@types/uuid": "8.3.4",