docs(tracing): clarify diff between test tracing and context.tracing (#35852)

docs/src/api/class-tracing.md

@@ -3,6 +3,12 @@
 
 API for collecting and saving Playwright traces. Playwright traces can be opened in [Trace Viewer](../trace-viewer.md) after Playwright script runs.
 
+:::note
+You probably want to [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead of using `context.tracing`.
+
+The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions (like `expect` calls). We recommend [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace), which includes those assertions and provides a more complete trace for debugging test failures.
+:::
+
 Start recording a trace before performing actions. At the end, stop tracing and save it to a file.
 
 ```js
@@ -11,6 +17,7 @@ const context = await browser.newContext();
 await context.tracing.start({ screenshots: true, snapshots: true });
 const page = await context.newPage();
 await page.goto('https://playwright.dev');
+expect(page.url()).toBe('https://playwright.dev');
 await context.tracing.stop({ path: 'trace.zip' });
 ```
 
@@ -66,12 +73,19 @@ await context.Tracing.StopAsync(new()
 
 Start tracing.
 
+:::note
+You probably want to [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead of using `Tracing.start`.
+
+The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions (like `expect` calls). We recommend [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace), which includes those assertions and provides a more complete trace for debugging test failures.
+:::
+
 **Usage**
 
 ```js
 await context.tracing.start({ screenshots: true, snapshots: true });
 const page = await context.newPage();
 await page.goto('https://playwright.dev');
+expect(page.url()).toBe('https://playwright.dev');
 await context.tracing.stop({ path: 'trace.zip' });
 ```
 

packages/playwright-client/types/types.d.ts

@@ -21175,6 +21175,15 @@ export interface Touchscreen {
  * API for collecting and saving Playwright traces. Playwright traces can be opened in
  * [Trace Viewer](https://playwright.dev/docs/trace-viewer) after Playwright script runs.
  *
+ * **NOTE** You probably want to
+ * [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead
+ * of using `context.tracing`.
+ *
+ * The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions
+ * (like `expect` calls). We recommend
+ * [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace),
+ * which includes those assertions and provides a more complete trace for debugging test failures.
+ *
  * Start recording a trace before performing actions. At the end, stop tracing and save it to a file.
  *
  * ```js
@@ -21183,6 +21192,7 @@ export interface Touchscreen {
  * await context.tracing.start({ screenshots: true, snapshots: true });
  * const page = await context.newPage();
  * await page.goto('https://playwright.dev');
+ * expect(page.url()).toBe('https://playwright.dev');
  * await context.tracing.stop({ path: 'trace.zip' });
  * ```
  *
@@ -21230,12 +21240,22 @@ export interface Tracing {
   /**
    * Start tracing.
    *
+   * **NOTE** You probably want to
+   * [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead
+   * of using `Tracing.start`.
+   *
+   * The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions
+   * (like `expect` calls). We recommend
+   * [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace),
+   * which includes those assertions and provides a more complete trace for debugging test failures.
+   *
    * **Usage**
    *
    * ```js
    * await context.tracing.start({ screenshots: true, snapshots: true });
    * const page = await context.newPage();
    * await page.goto('https://playwright.dev');
+   * expect(page.url()).toBe('https://playwright.dev');
    * await context.tracing.stop({ path: 'trace.zip' });
    * ```
    *

packages/playwright-core/types/types.d.ts

@@ -21175,6 +21175,15 @@ export interface Touchscreen {
  * API for collecting and saving Playwright traces. Playwright traces can be opened in
  * [Trace Viewer](https://playwright.dev/docs/trace-viewer) after Playwright script runs.
  *
+ * **NOTE** You probably want to
+ * [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead
+ * of using `context.tracing`.
+ *
+ * The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions
+ * (like `expect` calls). We recommend
+ * [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace),
+ * which includes those assertions and provides a more complete trace for debugging test failures.
+ *
  * Start recording a trace before performing actions. At the end, stop tracing and save it to a file.
  *
  * ```js
@@ -21183,6 +21192,7 @@ export interface Touchscreen {
  * await context.tracing.start({ screenshots: true, snapshots: true });
  * const page = await context.newPage();
  * await page.goto('https://playwright.dev');
+ * expect(page.url()).toBe('https://playwright.dev');
  * await context.tracing.stop({ path: 'trace.zip' });
  * ```
  *
@@ -21230,12 +21240,22 @@ export interface Tracing {
   /**
    * Start tracing.
    *
+   * **NOTE** You probably want to
+   * [enable tracing in your config file](https://playwright.dev/docs/api/class-testoptions#test-options-trace) instead
+   * of using `Tracing.start`.
+   *
+   * The `context.tracing` API captures browser operations and network activity, but it doesn't record test assertions
+   * (like `expect` calls). We recommend
+   * [enabling tracing through Playwright Test configuration](https://playwright.dev/docs/api/class-testoptions#test-options-trace),
+   * which includes those assertions and provides a more complete trace for debugging test failures.
+   *
    * **Usage**
    *
    * ```js
    * await context.tracing.start({ screenshots: true, snapshots: true });
    * const page = await context.newPage();
    * await page.goto('https://playwright.dev');
+   * expect(page.url()).toBe('https://playwright.dev');
    * await context.tracing.stop({ path: 'trace.zip' });
    * ```
    *