diff --git a/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11001.test.ts b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11001.test.ts
new file mode 100644
index 000000000..46ff09817
--- /dev/null
+++ b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11001.test.ts
@@ -0,0 +1,22 @@
+import { Express } from 'express'
+import { describe, it, beforeAll, assert } from 'vitest'
+
+import { initTests } from '../../../../utils'
+import { getCourseYearlyStats, CourseYearlyStats } from '../helpers'
+
+void describe('Course yearly attempt statistics - MAT11001 (no substitutions)', () => {
+  let app: Express
+  let body: CourseYearlyStats
+  beforeAll(async () => {
+    app = await initTests()
+    body = await getCourseYearlyStats(app, 'codes=MAT11001&combineSubstitutions=false')
+  })
+
+  it('should include every attempt of a student who has only failed the course', () => {
+    const stats = body.unifyStats?.statistics.find(year => year.name === '2018-2019')
+    assert(stats && 'enrollments' in stats, 'Missing field enrollment in statsitics')
+
+    assert.strictEqual(stats.attempts.categories.failed.length, 1, "Didn't include student's failed attempt")
+    assert.deepStrictEqual(stats.attempts.categories.failed, ['542874'], "Didn't include student's failed attempt")
+  })
+})
diff --git a/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11002.test.ts b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11002.test.ts
new file mode 100644
index 000000000..b97d01c5a
--- /dev/null
+++ b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat11002.test.ts
@@ -0,0 +1,44 @@
+import { Express } from 'express'
+import { describe, it, beforeAll, assert } from 'vitest'
+
+import { initTests } from '../../../../utils'
+import { getCourseYearlyStats, CourseYearlyStats } from '../helpers'
+
+void describe('Course yearly attempt statistics - MAT11002 (no substitutions)', () => {
+  let app: Express
+  let body: CourseYearlyStats
+  beforeAll(async () => {
+    app = await initTests()
+    body = await getCourseYearlyStats(app, 'codes=MAT11002&combineSubstitutions=false')
+  })
+
+  // FIXME: What is this even testing??
+  it.skip('should not include attempts for student with only AY credit (501716)', () => {
+    const stats = body.unifyStats?.statistics.find(year => year.name === '2017-2018')
+    assert(stats && 'enrollments' in stats, 'Missing field enrollment in statsitics')
+    assert.strictEqual(stats.attempts.categories.failed.length, 1)
+    assert.deepStrictEqual(stats.attempts.categories.failed, ['501716'])
+  })
+
+  it('should include a failed and a passed attempt for a student with both (501716)', () => {
+    const year = body.unifyStats?.statistics.find(year => year.name === '2018-2019')
+    assert(year && 'enrollments' in year, 'Stats missing completely')
+    assert.include(year.attempts.categories.failed, '501716', 'Failed attempts missing the student in question')
+    assert.include(year.attempts.categories.passed, '501716', "Passed attempts didn't include the passed attempt")
+    assert.include(year.attempts.grades['1'] ?? [], '501716', 'Grades should include the attempt in the correct grade')
+  })
+
+  it('should include an attempt with only approved grade (543385)', () => {
+    const year = body.unifyStats?.statistics.find(year => year.name === '2022-2023')
+    assert(year && 'enrollments' in year, 'Stats missing completely')
+    assert.notInclude(year.attempts.categories.failed, '543385')
+    assert.include(year.attempts.categories.passed, '543385', "Passed attempts didn't include the approved attempt")
+    assert.include(year.attempts.grades['5'] ?? [], '543385', 'Grades should include the attempt in the correct grade')
+  })
+
+  it('should include an attempt with only improved grade (509770)', () => {
+    const year = body.unifyStats?.statistics.find(year => year.name === '2018-2019')
+    assert(year && 'enrollments' in year, 'Missing stats for 2018-2019')
+    assert.include(year.attempts.categories.passed, '509770', 'Passed attempts should include in passed attempts')
+  })
+})
diff --git a/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat21003.test.ts b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat21003.test.ts
new file mode 100644
index 000000000..54f3f1354
--- /dev/null
+++ b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/mat21003.test.ts
@@ -0,0 +1,85 @@
+import { Express } from 'express'
+import { describe, it, beforeAll, assert } from 'vitest'
+
+import { yearToYearCode } from '@oodikone/shared/util'
+import { initTests } from '../../../../utils'
+import { getCourseYearlyStats, CourseYearlyStats } from '../helpers'
+
+void describe('Course yearly attempt statistics - MAT21003 (no substitutions)', () => {
+  let app: Express
+  beforeAll(async () => {
+    app = await initTests()
+  })
+
+  describe('duplicate failed attempts across a large timespan are counted separately', () => {
+    let body: CourseYearlyStats
+    beforeAll(async () => {
+      body = await getCourseYearlyStats(app, 'codes=MAT21003&combineSubstitutions=false')
+    })
+
+    it('2017-2018 should include a single failed attempt (539036)', () => {
+      const year = body.unifyStats?.statistics.find(year => year.name === '2017-2018')
+      assert(year && 'enrollments' in year, 'Missing stats for 2017-2018')
+      assert.deepStrictEqual(
+        year.attempts.categories.failed,
+        ['539036'],
+        'Failed attempts should not include any students'
+      )
+    })
+
+    it('2018-2019 should include a failed attempt (539036)', () => {
+      const year = body.unifyStats?.statistics.find(year => year.name === '2018-2019')
+      assert(year && 'enrollments' in year, 'Missing stats for 2018-2019')
+      assert.include(year.attempts.categories.failed, '539036', 'Failed attempts should include the failed attempt')
+    })
+  })
+
+  describe('year selection for smaller timeframes', () => {
+    it.each([
+      ['2017-2018', 2017, 2017],
+      ['2020-2023', 2020, 2022],
+      ['2016-2024', 2016, 2023],
+    ])('should include correct years for %s', async (name, from, to) => {
+      const body = await getCourseYearlyStats(
+        app,
+        `codes=MAT21003&combineSubstitutions=false&fromYearCode=${yearToYearCode(from)}&toYearCode=${yearToYearCode(to)}`
+      )
+
+      const years: string[] = []
+      for (let i = from; i <= to; i++) {
+        years.push(`${i}-${i + 1}`)
+      }
+      assert.deepStrictEqual(
+        body.unifyStats!.statistics.map(({ name }) => name),
+        years,
+        `${name} included incorrect years`
+      )
+    })
+  })
+
+  describe('duplicate attempts are counted again once an attempt falls out of the timespan', () => {
+    it('2017-2018 should include a failed attempt (539036)', async () => {
+      const body = await getCourseYearlyStats(
+        app,
+        `codes=MAT21003&combineSubstitutions=false&fromYearCode=${yearToYearCode(2017)}&toYearCode=${yearToYearCode(2017)}`
+      )
+      const year = body.unifyStats!.statistics.find(year => year.name === '2017-2018')
+      assert(year && 'enrollments' in year, 'Missing stats for 2017-2018')
+      assert.deepStrictEqual(
+        year.attempts.categories.failed,
+        ['539036'],
+        'Failed attempts should have included a student'
+      )
+    })
+
+    it('2018-2019 should include a failed attempt (539036)', async () => {
+      const body = await getCourseYearlyStats(
+        app,
+        `codes=MAT21003&combineSubstitutions=false&fromYearCode=${yearToYearCode(2018)}&toYearCode=${yearToYearCode(2018)}`
+      )
+      const year = body.unifyStats?.statistics.find(year => year.name === '2018-2019')
+      assert(year && 'enrollments' in year, 'Missing stats for 2018-2019')
+      assert.include(year.attempts.categories.failed, '539036', 'Failed attempts included the incorrect students')
+    })
+  })
+})
diff --git a/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/tkt10002.test.ts b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/tkt10002.test.ts
new file mode 100644
index 000000000..828749bca
--- /dev/null
+++ b/services/backend/tests/api/courses/courseYearlyStats/attemptStatistics/tkt10002.test.ts
@@ -0,0 +1,149 @@
+import { Express } from 'express'
+import { describe, it, beforeAll, assert } from 'vitest'
+
+import { yearToYearCode } from '@oodikone/shared/util'
+import { initTests } from '../../../../utils'
+import { getCourseYearlyStats, CourseYearlyStats } from '../helpers'
+
+void describe('Course yearly attempt statistics - TKT10002 (no substitutions)', () => {
+  let app: Express
+  beforeAll(async () => {
+    app = await initTests()
+  })
+
+  describe('full range (2016-2023)', () => {
+    let body: CourseYearlyStats
+    beforeAll(async () => {
+      body = await getCourseYearlyStats(
+        app,
+        `codes=TKT10002&combineSubstitutions=false&fromYearCode=${yearToYearCode(2016)}&toYearCode=${yearToYearCode(2023)}`
+      )
+    })
+
+    it('has one entry per statistic year', () => {
+      assert.strictEqual(body.unifyStats!.statistics.length, 8, 'unifyStats years')
+      assert.strictEqual(body.regularStats!.statistics.length, 8, 'regularStats years')
+      assert.strictEqual(body.openStats!.statistics.length, 4, 'openStats years')
+    })
+
+    it.each([
+      ['2016-2017', { total: 1, passed: 1, failed: 0 }, { 5: 0, 4: 1, 3: 0, 2: 0, 1: 0, 0: 0, 'Hyl.': 0, 'Hyv.': 0 }],
+      [
+        '2017-2018',
+        { total: 28, passed: 19, failed: 9 },
+        { 5: 11, 4: 5, 3: 2, 2: 1, 1: 0, 0: 0, 'Hyl.': 9, 'Hyv.': 0 },
+      ],
+      [
+        '2018-2019',
+        { total: 32, passed: 26, failed: 6 },
+        { 5: 18, 4: 3, 3: 2, 2: 1, 1: 2, 0: 5, 'Hyl.': 1, 'Hyv.': 0 },
+      ],
+      [
+        '2019-2020',
+        { total: 29, passed: 28, failed: 1 },
+        { 5: 17, 4: 5, 3: 1, 2: 4, 1: 1, 0: 0, 'Hyl.': 1, 'Hyv.': 0 },
+      ],
+      [
+        '2020-2021',
+        { total: 23, passed: 23, failed: 0 },
+        { 5: 18, 4: 2, 3: 0, 2: 2, 1: 0, 0: 0, 'Hyl.': 0, 'Hyv.': 1 },
+      ],
+      [
+        '2021-2022',
+        { total: 15, passed: 15, failed: 0 },
+        { 5: 13, 4: 2, 3: 0, 2: 0, 1: 0, 0: 0, 'Hyl.': 0, 'Hyv.': 0 },
+      ],
+      [
+        '2022-2023',
+        { total: 27, passed: 27, failed: 0 },
+        { 5: 21, 4: 6, 3: 0, 2: 0, 1: 0, 0: 0, 'Hyl.': 0, 'Hyv.': 0 },
+      ],
+      ['2023-2024', { total: 1, passed: 1, failed: 0 }, { 5: 1, 4: 0, 3: 0, 2: 0, 1: 0, 0: 0, 'Hyl.': 0, 'Hyv.': 0 }],
+    ])('for attempt statistic content during (%s)', (year, categories, grades) => {
+      const stats = body.unifyStats!.statistics.find(yearStats => yearStats.name === year)!
+      assert('enrollments' in stats, 'Missing field enrollment in statsitics')
+
+      assert.strictEqual(
+        stats.attempts.categories.failed.length,
+        categories.failed,
+        `Incorrect amount of failed attempts for ${year}`
+      )
+      assert.strictEqual(
+        stats.attempts.categories.passed.length,
+        categories.passed,
+        `Incorrect amount of passed attempts for ${year}`
+      )
+      assert.strictEqual(
+        stats.attempts.categories.failed.length + stats.attempts.categories.passed.length,
+        categories.total,
+        `Incorrect amount of total attempts for ${year}`
+      )
+
+      Object.entries(grades).forEach(([grade, count]) =>
+        assert.strictEqual(
+          stats.attempts.grades[grade]?.length ?? 0,
+          count,
+          `Incorrect amount of attempts with grade ${grade}`
+        )
+      )
+    })
+
+    it('should include every attempt of a student who has failed a course in 2017 and later completed it', () => {
+      const year2017 = body.unifyStats!.statistics.find(year => year.name === '2017-2018')
+      const year2018 = body.unifyStats!.statistics.find(year => year.name === '2018-2019')
+      const year2020 = body.unifyStats!.statistics.find(year => year.name === '2020-2021')
+      const year2022 = body.unifyStats!.statistics.find(year => year.name === '2022-2023')
+      assert(year2017 && 'enrollments' in year2017, 'Missing stats for 2017-2018')
+      assert(year2018 && 'enrollments' in year2018, 'Missing stats for 2018-2019')
+      assert(year2020 && 'enrollments' in year2020, 'Missing stats for 2020-2021')
+      assert(year2022 && 'enrollments' in year2022, 'Missing stats for 2021-2022')
+
+      assert.include(year2017.attempts.categories.failed, '457686')
+      assert.include(year2018.attempts.categories.passed, '457686')
+
+      assert.include(year2017.attempts.categories.failed, '455478')
+      assert.include(year2020.attempts.categories.passed, '455478')
+      assert.strictEqual(year2017.attempts.categories.failed.filter(sNum => sNum === '455478').length, 2) // Failed twice
+
+      assert.include(year2017.attempts.categories.failed, '547994')
+      assert.include(year2022.attempts.categories.passed, '547994')
+    })
+  })
+
+  describe('single academic year ranges', () => {
+    it.each([
+      // Same as above
+      ['2016-2017', { total: 1, passed: 1, failed: 0 }],
+      ['2017-2018', { total: 28, passed: 19, failed: 9 }],
+      ['2018-2019', { total: 32, passed: 26, failed: 6 }],
+      ['2019-2020', { total: 29, passed: 28, failed: 1 }],
+      ['2020-2021', { total: 23, passed: 23, failed: 0 }],
+      ['2021-2022', { total: 15, passed: 15, failed: 0 }],
+      ['2022-2023', { total: 27, passed: 27, failed: 0 }],
+      ['2023-2024', { total: 1, passed: 1, failed: 0 }],
+    ])('should include correct attempt stats for one academic year (%s)', async (year, categories) => {
+      const body = await getCourseYearlyStats(
+        app,
+        `codes=TKT10002&combineSubstitutions=false&fromYearCode=${yearToYearCode(year.split('-').at(0))}&toYearCode=${yearToYearCode(parseInt(year.split('-').at(1)!)) - 1}`
+      )
+      const stats = body.unifyStats!.statistics.find(yearStats => yearStats.name === year)!
+      assert('enrollments' in stats, 'Missing field enrollment in statsitics')
+
+      assert.strictEqual(
+        stats.attempts.categories.failed.length,
+        categories.failed,
+        `Incorrect amount of failed attempts for ${year}`
+      )
+      assert.strictEqual(
+        stats.attempts.categories.passed.length,
+        categories.passed,
+        `Incorrect amount of passed attempts for ${year}`
+      )
+      assert.strictEqual(
+        stats.attempts.categories.failed.length + stats.attempts.categories.passed.length,
+        categories.total,
+        `Incorrect amount of total attempts for ${year}`
+      )
+    })
+  })
+})