Fix test isolation, remove fake timers, cleanup low-value command tests

Test Isolation:
- Add `credentialsFile` parameter to ResolveConfigOptions and LoadConfigOptions
- Update MobifySource to use credentialsFile when provided (overrides ~/.mobify)
- Add --credentials-file flag with MRT_CREDENTIALS_FILE env var to MrtCommand
- Add config-isolation.ts helper to clear SFCC_*/MRT_* env vars for tests

Performance:
- Replace fake timers with pollInterval option in site-archive tests
- Fake timers conflict with MSW v2's microtask queue
- Remove @sinonjs/fake-timers dev dependency

Command Test Cleanup:
- Delete cartridge-command.test.ts (100% trivial delegation tests)
- Simplify base-command.test.ts (keep getExtraParams, catch tests)
- Simplify instance-command.test.ts (keep requireX, context tests)
- Simplify mrt-command.test.ts (keep requireMrtCredentials only)
- Simplify oauth-command.test.ts (keep parseAuthMethods, requireOAuthCredentials)
- Simplify ods-command.test.ts (keep odsClient lazy init tests)

Documentation:
- Update testing skill with config isolation, pollInterval patterns
- Add command test guidelines (what to test vs avoid)
- Remove general knowledge content (basic Mocha/Chai patterns)

Author: clavery

.claude/skills/testing/SKILL.md

@@ -244,9 +244,9 @@
   },
   "dependencies": {
     "archiver": "^7.0.1",
-    "fuse.js": "^7.0.0",
     "chokidar": "^5.0.0",
     "cliui": "^9.0.1",
+    "fuse.js": "^7.0.0",
     "glob": "^13.0.0",
     "i18next": "^25.6.3",
     "jszip": "^3.10.1",

packages/b2c-tooling-sdk/package.json

@@ -44,6 +44,8 @@ export interface LoadConfigOptions {
   configPath?: string;
   /** Cloud origin for MRT ~/.mobify lookup (e.g., https://cloud-staging.mobify.com) */
   cloudOrigin?: string;
+  /** Path to custom MRT credentials file (overrides default ~/.mobify) */
+  credentialsFile?: string;
 }
 
 /**
@@ -110,6 +112,7 @@ export function loadConfig(
     configPath: options.configPath,
     hostnameProtection: true,
     cloudOrigin: options.cloudOrigin,
+    credentialsFile: options.credentialsFile,
     sourcesBefore: pluginSources.before,
     sourcesAfter: pluginSources.after,
   });

packages/b2c-tooling-sdk/src/cli/config.ts

@@ -55,15 +55,21 @@ export abstract class MrtCommand<T extends typeof Command> extends BaseCommand<T
       description: `MRT cloud origin URL (default: ${DEFAULT_MRT_ORIGIN})`,
       env: 'SFCC_MRT_CLOUD_ORIGIN',
     }),
+    'credentials-file': Flags.string({
+      description: 'Path to MRT credentials file (overrides default ~/.mobify)',
+      env: 'MRT_CREDENTIALS_FILE',
+    }),
   };
 
   protected override loadConfiguration(): ResolvedConfig {
     const cloudOrigin = this.flags['cloud-origin'] as string | undefined;
+    const credentialsFile = this.flags['credentials-file'] as string | undefined;
 
     const options: LoadConfigOptions = {
       instance: this.flags.instance,
       configPath: this.flags.config,
       cloudOrigin, // MobifySource uses this to load ~/.mobify--[hostname] if set
+      credentialsFile, // Override path to MRT credentials file
     };
 
     const flagConfig: Partial<ResolvedConfig> = {

packages/b2c-tooling-sdk/src/cli/mrt-command.ts

@@ -41,7 +41,8 @@ export class MobifySource implements ConfigSource {
   private lastPath?: string;
 
   load(options: ResolveConfigOptions): NormalizedConfig | undefined {
-    const mobifyPath = this.getMobifyPath(options.cloudOrigin);
+    // Use explicit credentialsFile if provided, otherwise use default path
+    const mobifyPath = options.credentialsFile ?? this.getMobifyPath(options.cloudOrigin);
     this.lastPath = mobifyPath;
 
     if (!fs.existsSync(mobifyPath)) {

packages/b2c-tooling-sdk/src/config/sources/mobify-source.ts

@@ -123,6 +123,8 @@ export interface ResolveConfigOptions {
   hostnameProtection?: boolean;
   /** Cloud origin for ~/.mobify lookup (MRT) */
   cloudOrigin?: string;
+  /** Path to custom MRT credentials file (overrides default ~/.mobify) */
+  credentialsFile?: string;
 
   /**
    * Custom sources to add BEFORE default sources (higher priority).