[OPIK-8011] [QA] test: e2e coverage for online evaluation sampling rate

apps/opik-frontend/src/shared/SliderInputControl/SliderInputControl.tsx

@@ -105,6 +105,7 @@ const SliderInputControl = ({
           )}
           <Input
             id={inputId}
+            data-testid={inputId}
             className="box-content w-[var(--input-width)] max-w-[5ch] border px-2 py-0 text-right [&:not(:focus)]:border-transparent [&:not(:focus)]:px-0.5"
             style={
               {

apps/opik-frontend/src/v2/pages-shared/automations/AddEditRuleDialog/RuleFilteringSection.tsx

@@ -426,7 +426,10 @@ const RuleFilteringSection: React.FC<RuleFilteringSectionProps> = ({
       className="-mb-4 w-full border-t border-border"
     >
       <AccordionItem value="filtering-sampling" className="border-none">
-        <AccordionTrigger className="px-3 py-2 hover:no-underline">
+        <AccordionTrigger
+          className="px-3 py-2 hover:no-underline"
+          data-testid="add-edit-rule-dialog-filtering-sampling-trigger"
+        >
           <div className="flex items-center gap-1">
             <Label className="text-sm font-medium">Filtering & Sampling</Label>
             <ExplainerIcon

tests_end_to_end/coverage/taxonomy.yaml

@@ -628,6 +628,7 @@ areas:
       - online-evaluation/online-evaluation-smoke.spec.ts
       - online-evaluation/online-evaluation-delete-rule.spec.ts
       - online-evaluation/online-evaluation-enable-disable-rule.spec.ts
+      - online-evaluation/online-evaluation-sampling-rate.spec.ts
     capabilities:
       create-llm-judge-rule:   { covered: true,  tier: t1-smoke }
       llm-judge-scores:        { covered: true,  tier: t1-smoke, note: "bimodal safe/unsafe" }
@@ -637,7 +638,7 @@ areas:
       list-rules:              { covered: false }
       rule-scope-thread-span:  { covered: false, note: "span/thread scope flags" }
       rule-filters:            { covered: false }
-      sampling-rate:           { covered: false }
+      sampling-rate:           { covered: true,  tier: t2-cuj, note: "50% rule vs 100% control over one 30-trace batch; binomial band 15-85%" }
       clone-rule:              { covered: false }
       edit-rule:               { covered: false }
       enable-disable-rule:     { covered: true,  tier: t2-cuj, note: "edit-dialog switch; control rule proves scoring stopped, then resumed" }

tests_end_to_end/e2e/core/backend/client.ts

@@ -88,6 +88,12 @@ export interface AutomationRuleRef {
   name: string;
   projectIds: string[];
   enabled: boolean;
+  /**
+   * Fraction in [0, 1] — the backend's own units. The dialog shows a
+   * percentage (50), the API stores a fraction (0.5); assertions must use the
+   * fraction.
+   */
+  samplingRate: number;
 }
 
 export interface AnnotationQueueReviewerRef {
@@ -222,6 +228,23 @@ export function makeBackendClient(apiKey: string | null = null) {
     }
   };
 
+  /**
+   * The generated REST type marks `samplingRate` optional. Defaulting a missing
+   * value to 1 would present as "100% of traces", which is indistinguishable
+   * from a correctly-configured full-rate rule — so a sampling assertion built
+   * on that default could pass while the field was never returned at all.
+   * Fail loudly instead.
+   */
+  const requireSamplingRate = (rate: number | undefined, ruleName: string): number => {
+    if (typeof rate !== 'number' || Number.isNaN(rate)) {
+      throw new Error(
+        `listAutomationRulesForProject: rule '${ruleName}' returned no samplingRate — ` +
+          `cannot assert on sampling behaviour.`,
+      );
+    }
+    return rate;
+  };
+
   // Hoisted so pollTraceForFeedbackScore (a free function) can call it without
   // depending on the not-yet-constructed return object.
   const localGetTrace = async (traceId: string): Promise<TraceDetail | null> => {
@@ -544,6 +567,7 @@ export function makeBackendClient(apiKey: string | null = null) {
         name: r.name,
         projectIds: (r.projects ?? []).map((p) => String(p.projectId)),
         enabled: r.enabled ?? true,
+        samplingRate: requireSamplingRate(r.samplingRate, r.name),
       }));
     },
 

tests_end_to_end/e2e/pom/online-evaluation.page.ts

@@ -14,6 +14,11 @@ export interface CreateRuleDialogPythonEqualsFields {
   name: string;
   /** The literal string the trace's output must equal to score 1.0. */
   referenceValue: string;
+  /**
+   * Sampling rate as the PERCENTAGE shown in the dialog (0-100), not the
+   * fraction the API stores. Omit to leave the control at its 100% default.
+   */
+  samplingRatePercent?: number;
 }
 
 /**
@@ -132,6 +137,77 @@ export class OnlineEvaluationPage {
     return this.ruleRow(name).getByRole('cell', { name: status, exact: true });
   }
 
+  /**
+   * The Sampling rate cell for a rule row, rendered by OnlineEvaluationPage's
+   * `sampling_rate` column as a formatted percentage ("50%", "100%") — note the
+   * list shows a PERCENTAGE while the API stores a fraction.
+   */
+  ruleSamplingRateCell(name: string, displayValue: string): Locator {
+    return this.ruleRow(name).getByRole('cell', { name: displayValue, exact: true });
+  }
+
+  /**
+   * The "Filtering & Sampling" accordion inside the add/edit dialog. It renders
+   * COLLAPSED by default, and its content is unmounted while collapsed, so the
+   * sampling-rate control does not exist until this is expanded.
+   */
+  get filteringSamplingTrigger(): Locator {
+    return this.dialog.getByTestId('add-edit-rule-dialog-filtering-sampling-trigger');
+  }
+
+  /**
+   * The sampling-rate number input (the percentage box next to the slider).
+   * SliderInputControl derives this testid from its `id` prop.
+   */
+  get samplingRateInput(): Locator {
+    return this.dialog.getByTestId('sampling_rate-input');
+  }
+
+  /**
+   * Expand the Filtering & Sampling accordion, if it is not already open.
+   * Idempotent: switching the rule TYPE re-renders the dialog body but leaves
+   * the accordion open, so callers can invoke this without tracking state.
+   */
+  async expandFilteringAndSampling(): Promise<void> {
+    return test.step('expand the Filtering & Sampling accordion', async () => {
+      const trigger = this.filteringSamplingTrigger;
+      await trigger.waitFor({ state: 'visible' });
+      if ((await trigger.getAttribute('aria-expanded')) !== 'true') {
+        await trigger.click();
+      }
+      await expect(trigger).toHaveAttribute('aria-expanded', 'true');
+      await this.samplingRateInput.waitFor({ state: 'visible' });
+    });
+  }
+
+  /**
+   * Set the sampling rate to a PERCENTAGE (0-100), as the dialog displays it.
+   *
+   * The blur is load-bearing, not defensive tidying. SliderInputControl commits
+   * the typed value to the form in `onBlur` (`validateAndHandleChange`), NOT in
+   * `onChange` — so filling the box and submitting straight away posts the
+   * PREVIOUS value. Verified against the live dialog: typing 25 and submitting
+   * without blurring persists `sampling_rate: 1.0`, silently discarding the
+   * input. That failure is invisible to a sampling assertion (a rule left at
+   * 100% scores everything, which is exactly what "sampling ignored" looks
+   * like), so the commit has to be forced here.
+   *
+   * Do not "verify" the value by reading the slider's `aria-valuenow`: the
+   * slider mirrors the component's local state, so it reports the typed number
+   * even when the form value is still stale. The only trustworthy check is the
+   * persisted rate on the created rule — assert that in the test.
+   */
+  async setSamplingRatePercent(percent: number): Promise<void> {
+    return test.step(`set sampling rate to ${percent}%`, async () => {
+      await this.expandFilteringAndSampling();
+      const input = this.samplingRateInput;
+      await input.fill(String(percent));
+      // Commit via blur — see the note above; without this the value is dropped.
+      await input.blur();
+      await expect(input).toHaveValue(String(percent));
+    });
+  }
+
   /** The "Enable rule" switch inside the add/edit dialog. */
   get enableRuleSwitch(): Locator {
     return this.dialog.getByRole('switch', { name: 'Enable rule' });
@@ -254,6 +330,13 @@ export class OnlineEvaluationPage {
     // input to settle to the new shape, then override its path.
     await this.setVariableMapping('output', 'output.output');
 
+    // Set the rate last: the sampling control lives in a collapsed accordion
+    // below the code editor, and switching TYPE / re-parsing the snippet
+    // re-renders the body above it.
+    if (fields.samplingRatePercent !== undefined) {
+      await this.setSamplingRatePercent(fields.samplingRatePercent);
+    }
+
     await d.getByTestId('add-edit-rule-dialog-submit').click();
     await d.waitFor({ state: 'hidden' });
   }