diff --git a/packages/cli-kit/src/private/common/array.test.ts b/packages/cli-kit/src/private/common/array.test.ts
new file mode 100644
index 00000000000..0f286746ee4
--- /dev/null
+++ b/packages/cli-kit/src/private/common/array.test.ts
@@ -0,0 +1,40 @@
+import {unionArrayStrategy} from './array.js'
+import {describe, test, expect} from 'vitest'
+
+describe('unionArrayStrategy', () => {
+  test('combines two arrays and removes duplicates', () => {
+    // Given
+    const destination = ['a', 'b']
+    const source = ['b', 'c']
+
+    // When
+    const result = unionArrayStrategy(destination, source)
+
+    // Then
+    expect(result).toEqual(['a', 'b', 'c'])
+  })
+
+  test('handles empty arrays', () => {
+    // Given
+    const destination: unknown[] = []
+    const source = [1, 2]
+
+    // When
+    const result = unionArrayStrategy(destination, source)
+
+    // Then
+    expect(result).toEqual([1, 2])
+  })
+
+  test('handles non-overlapping arrays', () => {
+    // Given
+    const destination = [1, 2]
+    const source = [3, 4]
+
+    // When
+    const result = unionArrayStrategy(destination, source)
+
+    // Then
+    expect(result).toEqual([1, 2, 3, 4])
+  })
+})