add failing test

Author: jycouet

test/unit/app/utils/download-anomalies.spec.ts

@@ -2,49 +2,31 @@ import { describe, expect, it } from 'vitest'
 import { applyBlocklistCorrection } from '../../../../app/utils/download-anomalies'
 import type { WeeklyDataPoint } from '../../../../app/types/chart'
 
+/** Helper to build a WeeklyDataPoint from a start date and value. */
+function week(weekStart: string, value: number): WeeklyDataPoint {
+  const start = new Date(`${weekStart}T00:00:00Z`)
+  const end = new Date(start)
+  end.setUTCDate(end.getUTCDate() + 6)
+  const weekEnd = end.toISOString().slice(0, 10)
+  return {
+    value,
+    weekKey: `${weekStart}_${weekEnd}`,
+    weekStart,
+    weekEnd,
+    timestampStart: start.getTime(),
+    timestampEnd: end.getTime(),
+  }
+}
+
 describe('applyBlocklistCorrection', () => {
-  it('treats overlapping weekly buckets as affected anomalies', () => {
-    const data: WeeklyDataPoint[] = [
-      {
-        value: 100,
-        weekKey: '2022-11-07_2022-11-13',
-        weekStart: '2022-11-07',
-        weekEnd: '2022-11-13',
-        timestampStart: 0,
-        timestampEnd: 0,
-      },
-      {
-        value: 999,
-        weekKey: '2022-11-14_2022-11-20',
-        weekStart: '2022-11-14',
-        weekEnd: '2022-11-20',
-        timestampStart: 0,
-        timestampEnd: 0,
-      },
-      {
-        value: 999,
-        weekKey: '2022-11-21_2022-11-27',
-        weekStart: '2022-11-21',
-        weekEnd: '2022-11-27',
-        timestampStart: 0,
-        timestampEnd: 0,
-      },
-      {
-        value: 999,
-        weekKey: '2022-11-28_2022-12-04',
-        weekStart: '2022-11-28',
-        weekEnd: '2022-12-04',
-        timestampStart: 0,
-        timestampEnd: 0,
-      },
-      {
-        value: 200,
-        weekKey: '2022-12-05_2022-12-11',
-        weekStart: '2022-12-05',
-        weekEnd: '2022-12-11',
-        timestampStart: 0,
-        timestampEnd: 0,
-      },
+  // Anomaly Nov 2022: start=2022-11-15, end=2022-11-30
+  it('corrects weeks overlapping the anomaly', () => {
+    const data = [
+      week('2022-11-07', 100),
+      week('2022-11-14', 999),
+      week('2022-11-21', 999),
+      week('2022-11-28', 999),
+      week('2022-12-05', 200),
     ]
 
     expect(
@@ -61,4 +43,51 @@ describe('applyBlocklistCorrection', () => {
       data[4],
     ])
   })
+
+  // Anomaly Jun 2023: start=2023-06-19, end=2023-06-22
+  it('does not over-correct a week starting on the anomaly end boundary', () => {
+    const data = [
+      week('2023-06-01', 500_000),
+      week('2023-06-08', 500_000),
+      week('2023-06-15', 10_000_000), // contains spike
+      week('2023-06-22', 500_000), // starts on anomaly end boundary — normal!
+      week('2023-06-29', 500_000),
+    ]
+
+    const result = applyBlocklistCorrection({
+      data,
+      packageName: 'svelte',
+      granularity: 'weekly',
+    }) as WeeklyDataPoint[]
+
+    // The spike week must be corrected
+    expect(result[2]!.hasAnomaly).toBe(true)
+    expect(result[2]!.value).toBeLessThan(1_000_000)
+
+    // The boundary week must NOT be modified
+    expect(result[3]!.value).toBe(500_000)
+    expect(result[3]!.hasAnomaly).toBeUndefined()
+  })
+
+  it('does not over-correct a week ending on the anomaly start boundary', () => {
+    const data = [
+      week('2023-06-13', 500_000), // ends on anomaly start boundary — normal!
+      week('2023-06-20', 10_000_000), // contains spike
+      week('2023-06-27', 500_000),
+    ]
+
+    const result = applyBlocklistCorrection({
+      data,
+      packageName: 'svelte',
+      granularity: 'weekly',
+    }) as WeeklyDataPoint[]
+
+    // The boundary week must NOT be modified
+    expect(result[0]!.value).toBe(500_000)
+    expect(result[0]!.hasAnomaly).toBeUndefined()
+
+    // The spike week must be corrected
+    expect(result[1]!.hasAnomaly).toBe(true)
+    expect(result[1]!.value).toBeLessThan(1_000_000)
+  })
 })