test(star): add StarsLoaderTest test class to test StarsLoader

app/src/test/java/com/github/lookupgroup27/lookup/model/map/stars/StarsLoaderTest.kt

@@ -0,0 +1,45 @@
+package com.github.lookupgroup27.lookup.model.map.stars
+
+import android.content.Context
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mockito.*
+
+class StarsLoaderTest {
+
+  private lateinit var mockContext: Context
+  private lateinit var mockRepository: StarDataRepository
+  private lateinit var starsLoader: StarsLoader
+
+  @Before
+  fun setUp() {
+    mockContext = mock(Context::class.java)
+    mockRepository = mock(StarDataRepository::class.java)
+    starsLoader = StarsLoader(mockContext, mockRepository)
+  }
+
+  @Test
+  fun testLoadStars_callsUpdateStarPositions() {
+    // Arrange: Set up the mock repository
+    `when`(mockRepository.getUpdatedStars()).thenReturn(emptyList())
+
+    // Act: Call loadStars
+    starsLoader.loadStars()
+
+    // Assert: Verify that updateStarPositions was called
+    verify(mockRepository).updateStarPositions()
+  }
+
+  @Test
+  fun testLoadStars_handlesEmptyStarDataList() {
+    // Arrange: Return an empty star data list
+    `when`(mockRepository.getUpdatedStars()).thenReturn(emptyList())
+
+    // Act: Call loadStars
+    val stars = starsLoader.loadStars()
+
+    // Assert: Verify the result is an empty list
+    assertEquals(0, stars.size)
+  }
+}