fix: remove ±0 delta indicators from report templates (#274)

When previous run data exists but values haven't changed, the reports
were showing ±0 next to every metric. This was noisy and unhelpful.
Now only actual changes (↑/↓) are displayed.

Affected templates:
- summary-delta-table.hbs
- github.hbs
- fail-rate-table.hbs
- flaky-rate-table.hbs

Closes #273

Author: alexshamrai

__tests__/reports/delta-display.test.ts

@@ -0,0 +1,253 @@
+import Handlebars from 'handlebars'
+import { registerAllHelpers } from '../../src/handlebars/helpers'
+import * as fs from 'fs'
+import * as path from 'path'
+
+// Register project's own helpers (string, array, math, ansi helpers)
+beforeAll(() => {
+  registerAllHelpers()
+
+  // Register real implementations of helpers that handlebars-helpers-ctrf
+  // would normally provide (the package is mocked to no-op in Jest config)
+  Handlebars.registerHelper('gt', (a: number, b: number) => a > b)
+  Handlebars.registerHelper('lt', (a: number, b: number) => a < b)
+  Handlebars.registerHelper('abs', (a: number) => Math.abs(a))
+  Handlebars.registerHelper(
+    'toPercent',
+    (value: number, decimals: number = 2) => (value * 100).toFixed(decimals)
+  )
+  Handlebars.registerHelper('formatDuration', (d: number) => `${d}ms`)
+  Handlebars.registerHelper(
+    'formatDurationFromTimes',
+    (start: number, stop: number) => `${stop - start}ms`
+  )
+  Handlebars.registerHelper('addAll', (...args: unknown[]) => {
+    const values = args.slice(0, -1) as number[]
+    return values.reduce((sum, v) => sum + (v ?? 0), 0)
+  })
+  Handlebars.registerHelper('add', (a: number, b: number) => a + b)
+  Handlebars.registerHelper(
+    'countFlakyTests',
+    (tests: Array<{ flaky?: boolean }>) =>
+      tests?.filter((t) => t.flaky).length ?? 0
+  )
+  Handlebars.registerHelper(
+    'sortTestsByFailRate',
+    (tests: Array<Record<string, unknown>>) => tests ?? []
+  )
+  Handlebars.registerHelper(
+    'sortTestsByFlakyRate',
+    (tests: Array<Record<string, unknown>>) => tests ?? []
+  )
+  Handlebars.registerHelper('getCtrfEmoji', () => '')
+})
+
+function compileTemplate(
+  templatePath: string,
+  context: Record<string, unknown>
+): string {
+  const source = fs.readFileSync(
+    path.resolve(__dirname, '../../src/reports', templatePath),
+    'utf-8'
+  )
+  const template = Handlebars.compile(source, { preventIndent: true })
+  return template(context)
+}
+
+describe('summary-delta-table.hbs delta display', () => {
+  function makeContext(change: number) {
+    return {
+      ctrf: {
+        summary: {
+          tests: 10,
+          passed: 8,
+          failed: 1,
+          skipped: 1,
+          pending: 0,
+          other: 0,
+          start: 0,
+          stop: 1000
+        },
+        tests: []
+      },
+      report: {
+        results: {
+          summary: {
+            tests: 10,
+            passed: 8,
+            failed: 1,
+            skipped: 1,
+            pending: 0,
+            other: 0,
+            start: 0,
+            stop: 1000
+          }
+        },
+        insights: {
+          extra: {
+            summary: {
+              tests: { current: 10, baseline: 10 - change, change },
+              passed: { current: 8, baseline: 8 - change, change },
+              failed: { current: 1, baseline: 1, change: 0 },
+              skipped: { current: 1, baseline: 1, change: 0 },
+              other: { current: 0, baseline: 0, change: 0 },
+              flaky: { current: 0, baseline: 0, change: 0 },
+              duration: { current: 1000, baseline: 1000, change: 0 }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  it('should show ↑ for positive change', () => {
+    const result = compileTemplate('summary-delta-table.hbs', makeContext(3))
+    expect(result).toContain('↑3')
+  })
+
+  it('should show ↓ for negative change', () => {
+    const result = compileTemplate('summary-delta-table.hbs', makeContext(-2))
+    expect(result).toContain('↓2')
+  })
+
+  it('should not show ±0 for zero change', () => {
+    const result = compileTemplate('summary-delta-table.hbs', makeContext(0))
+    expect(result).not.toContain('±0')
+    expect(result).not.toContain('↑')
+    expect(result).not.toContain('↓')
+  })
+})
+
+describe('github.hbs delta display', () => {
+  function makeContext(change: number) {
+    return {
+      ctrf: {
+        summary: {
+          tests: 10,
+          passed: 8,
+          failed: 1,
+          skipped: 1,
+          pending: 0,
+          other: 0,
+          start: 0,
+          stop: 1000
+        },
+        tests: []
+      },
+      report: {
+        insights: {
+          extra: {
+            summary: {
+              failed: { change },
+              passed: { change },
+              skipped: { change: 0 },
+              pending: { change: 0 },
+              other: { change: 0 },
+              flaky: { change: 0 },
+              tests: { change },
+              duration: { change: 0 }
+            }
+          }
+        }
+      },
+      github: {}
+    }
+  }
+
+  it('should show ↑ for positive change', () => {
+    const result = compileTemplate('github.hbs', makeContext(3))
+    expect(result).toContain('↑3')
+  })
+
+  it('should show ↓ for negative change', () => {
+    const result = compileTemplate('github.hbs', makeContext(-2))
+    expect(result).toContain('↓2')
+  })
+
+  it('should not show ±0 for zero change', () => {
+    const result = compileTemplate('github.hbs', makeContext(0))
+    expect(result).not.toContain('±0')
+  })
+})
+
+describe('fail-rate-table.hbs delta display', () => {
+  function makeContext(change: number) {
+    return {
+      ctrf: {
+        tests: [
+          {
+            name: 'test1',
+            status: 'passed',
+            insights: {
+              failRate: { current: 0.1, change },
+              extra: {
+                totalResults: 10,
+                totalResultsPassed: 9,
+                totalResultsFailed: 1
+              }
+            }
+          }
+        ]
+      },
+      report: {
+        insights: {
+          failRate: { current: 0.1, change }
+        }
+      }
+    }
+  }
+
+  it('should show ↑ for positive fail rate change', () => {
+    const result = compileTemplate('fail-rate-table.hbs', makeContext(0.05))
+    expect(result).toContain('↑')
+  })
+
+  it('should show ↓ for negative fail rate change', () => {
+    const result = compileTemplate('fail-rate-table.hbs', makeContext(-0.05))
+    expect(result).toContain('↓')
+  })
+
+  it('should not show ±0 for zero fail rate change', () => {
+    const result = compileTemplate('fail-rate-table.hbs', makeContext(0))
+    expect(result).not.toContain('±0')
+  })
+})
+
+describe('flaky-rate-table.hbs delta display', () => {
+  function makeContext(change: number) {
+    return {
+      ctrf: {
+        tests: [
+          {
+            name: 'test1',
+            status: 'passed',
+            insights: {
+              flakyRate: { current: 0.1, change },
+              extra: { totalResults: 10, totalAttemptsFlaky: 1 }
+            }
+          }
+        ]
+      },
+      report: {
+        insights: {
+          flakyRate: { current: 0.1, change }
+        }
+      }
+    }
+  }
+
+  it('should show ↑ for positive flaky rate change', () => {
+    const result = compileTemplate('flaky-rate-table.hbs', makeContext(0.05))
+    expect(result).toContain('↑')
+  })
+
+  it('should show ↓ for negative flaky rate change', () => {
+    const result = compileTemplate('flaky-rate-table.hbs', makeContext(-0.05))
+    expect(result).toContain('↓')
+  })
+
+  it('should not show ±0 for zero flaky rate change', () => {
+    const result = compileTemplate('flaky-rate-table.hbs', makeContext(0))
+    expect(result).not.toContain('±0')
+  })
+})