💥 Add testdouble stubbing chained methods example

Author: YenHub

docs/engineering/javascript/test-double/stubbing-chained-methods.md

@@ -0,0 +1,29 @@
+# TestDouble.js: Stubbing Chained Methods
+
+```typescript
+td.replace(
+  config.getOptionalConfig,
+  'getOptionalConfig',
+  td.function('config.getOptionalConfig'),
+)
+
+td.when(config.getOptionalConfig(configKey)).thenReturn({
+  getOptionalString: td.function('getOptionalString'),
+})
+
+const configStubs = [
+  { key: 'athenaRoleArn', value: 'arn:aws:iam::123456789:role/dummy-role' },
+  { key: 'athenaRegion', value: 'dummy-region' },
+  { key: 'athenaRoleSessionName', value: 'dummy-session-name' },
+  { key: 'athenaCatalogName', value: 'dummy-catalog-name' },
+  { key: 'athenaDatabaseName', value: 'dummy-database-name' },
+  { key: 'athenaTableName', value: 'dummy-table-name' },
+  { key: 'athenaResultOutputLocation', value: 'dummy-output-location' },
+]
+
+configStubs.forEach(({ key, value }) =>
+  td
+    .when(config.getOptionalConfig(configKey).getOptionalString(key))
+    .thenReturn(value),
+)
+```

mkdocs.yml

@@ -68,6 +68,7 @@ nav:
               - NPKill - node_modules: engineering/javascript/node/node-cleanup.md
           - Jest:
               - Helpful Tips: engineering/javascript/jest/helpful-tips.md
+              - Stubbing Chained Methods: engineering/javascript/test-double/stubbing-chained-methods.md
       - Ruby:
           - Handling JSON: engineering/ruby/handling-json.md
       - Git: