test: add unit tests for getSnapAlignOffset utility

Author: ismail9k

src/utils/getSnapAlignOffset.spec.ts

@@ -0,0 +1,100 @@
+import { describe, expect, test } from 'vitest'
+
+import { getSnapAlignOffset } from './getSnapAlignOffset'
+
+describe('getSnapAlignOffset', () => {
+  describe('with itemsToShow parameter', () => {
+    test('should return correct offset for start alignment', () => {
+      expect(getSnapAlignOffset({ align: 'start', itemsToShow: 3 })).toBe(0)
+    })
+
+    test('should return correct offset for center/center-odd alignment', () => {
+      expect(getSnapAlignOffset({ align: 'center', itemsToShow: 3 })).toBe(1)
+      expect(getSnapAlignOffset({ align: 'center-odd', itemsToShow: 5 })).toBe(2)
+    })
+
+    test('should return correct offset for center-even alignment', () => {
+      expect(getSnapAlignOffset({ align: 'center-even', itemsToShow: 4 })).toBe(1)
+    })
+
+    test('should return correct offset for end alignment', () => {
+      expect(getSnapAlignOffset({ align: 'center-even', itemsToShow: 4 })).toBe(1)
+    })
+  })
+
+  describe('with slideSize and viewportSize parameters', () => {
+    test('should return correct offset for start alignment', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'start',
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(0)
+    })
+
+    test('should return correct offset for center/center-odd alignment', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'center',
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(300)
+
+      expect(
+        getSnapAlignOffset({
+          align: 'center-odd',
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(300)
+    })
+
+    test('should return correct offset for center-even alignment', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'center-even',
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(200)
+    })
+
+    test('should return correct offset for end alignment', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'end',
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(600)
+    })
+  })
+
+  describe('edge cases', () => {
+    test('should return 0 when no parameters provided', () => {
+      expect(getSnapAlignOffset({ align: 'start' })).toBe(0)
+    })
+
+    test('should return 0 for invalid alignment', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'invalid' as any,
+          slideSize: 200,
+          viewportSize: 800,
+        })
+      ).toBe(0)
+    })
+
+    test('should handle equal viewport and slide sizes', () => {
+      expect(
+        getSnapAlignOffset({
+          align: 'center',
+          slideSize: 800,
+          viewportSize: 800,
+        })
+      ).toBe(0)
+    })
+  })
+})