Added unit-tests for CacheController (#3275)

app/src/test/kotlin/fr/free/nrw/commons/cache/CacheControllerTest.kt

@@ -0,0 +1,48 @@
+package fr.free.nrw.commons.cache
+
+import com.github.varunpant.quadtree.Point
+import com.github.varunpant.quadtree.QuadTree
+import com.nhaarman.mockito_kotlin.verify
+import fr.free.nrw.commons.caching.CacheController
+import org.junit.Before
+import org.junit.Test
+import org.mockito.ArgumentMatchers
+import org.mockito.Mock
+import org.mockito.Mockito
+import org.mockito.MockitoAnnotations
+
+class CacheControllerTest {
+    /**
+     * initial setup, test environment
+     */
+    private lateinit var cacheController: CacheController
+
+    @Mock
+    private lateinit var quadTree: QuadTree<List<String>>
+
+    private lateinit var points: Array<Point<List<String>>>
+
+    var value = ArrayList<String>()
+
+
+    @Before
+    @Throws(Exception::class)
+    fun setUp() {
+        MockitoAnnotations.initMocks(this)
+        val point = Point<List<String>>(1.0, 1.0, value)
+        points = arrayOf(point)
+        value.add("1")
+        cacheController = CacheController(quadTree)
+        Mockito.`when`(quadTree.searchWithin(ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble())).thenReturn(points)
+    }
+
+    /**
+     * Test find category
+     */
+    @Test
+    fun testFindCategory() {
+        val findCategory = cacheController.findCategory()
+        verify(quadTree).searchWithin(ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble(), ArgumentMatchers.anyDouble())
+        assert(findCategory.size == 1)
+    }
+}