Add test code in GetFollowableTopicsUseCaseTest.kt([android#1327])

core/domain/src/test/kotlin/com/google/samples/apps/nowinandroid/core/domain/GetRecentSearchQueriesUseCaseTest.kt

@@ -18,7 +18,12 @@ package com.google.samples.apps.nowinandroid.core.domain
 
 import com.google.samples.apps.nowinandroid.core.testing.repository.TestRecentSearchRepository
 import com.google.samples.apps.nowinandroid.core.testing.util.MainDispatcherRule
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
 import org.junit.Rule
+import org.junit.Test
+import kotlin.test.assertEquals
 
 class GetRecentSearchQueriesUseCaseTest {
 
@@ -27,5 +32,81 @@ class GetRecentSearchQueriesUseCaseTest {
 
     private val recentSearchRepository = TestRecentSearchRepository()
 
+    private val useCase = GetRecentSearchQueriesUseCase(
+        recentSearchRepository
+    )
 
-}
+    @Test
+    fun whenNoParams_recentSearchQueriesAreReturnedUpTo10() = runTest {
+        // Obtain a stream of recent search queries with no param.
+        val recentSearchQueries = useCase()
+
+        // insert 5 search queries.
+        for (index in 0 until 5) {
+            recentSearchRepository.insertOrReplaceRecentSearch(testRecentSearchQueries[index])
+            // delay for saving value
+            delay(10L)
+        }
+
+        // Check that 5 recent search queries are ordered by latest.
+        assertEquals(
+            testRecentSearchQueries.take(5).reversed(),
+            recentSearchQueries.first().map { it.query },
+        )
+
+        // insert 9 more search queries.
+        for (index in 5 until testRecentSearchQueries.size) {
+            recentSearchRepository.insertOrReplaceRecentSearch(testRecentSearchQueries[index])
+            // delay for saving value
+            delay(10L)
+        }
+
+        // Check that recent search queries are ordered by latest up to 10.
+        assertEquals(
+            testRecentSearchQueries.reversed().take(10),
+            recentSearchQueries.first().map { it.query },
+        )
+    }
+
+    @Test
+    fun whenParamIsSetTo5_recentSearchQueriesAreReturnedUpTo5() = runTest {
+        // Obtain a stream of recent search queries with param set 5.
+        val recentSearchQueries = useCase(5)
+
+        // insert 2 search queries.
+        for (index in 0 until 2) {
+            recentSearchRepository.insertOrReplaceRecentSearch(testRecentSearchQueries[index])
+            // delay for saving value
+            delay(10L)
+        }
+
+        // Check that 5 recent search queries are ordered by latest.
+        assertEquals(
+            testRecentSearchQueries.take(2).reversed(),
+            recentSearchQueries.first().map { it.query },
+        )
+
+        // insert 12 more search queries.
+        for (index in 2 until testRecentSearchQueries.size) {
+            recentSearchRepository.insertOrReplaceRecentSearch(testRecentSearchQueries[index])
+            // delay for saving value
+            delay(10L)
+        }
+
+        // Check that recent search queries are ordered by latest up to 5.
+        assertEquals(
+            testRecentSearchQueries.reversed().take(5),
+            recentSearchQueries.first().map { it.query },
+        )
+    }
+}
+
+private val testRecentSearchQueries = listOf(
+    "Compose", "Wear OS",
+    "Jetpack", "Headlines",
+    "Architecture", "UI",
+    "Testing", "Android Studio",
+    "Performance", "New API",
+    "Games", "Android TV",
+    "Camera", "Media"
+)