Add test for flow use case 1

Author: LukasLechnerDev

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase1/FakeStockPriceDataSource.kt

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+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase1
+
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.Stock
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.asSharedFlow
+
+class FakeStockPriceDataSource : StockPriceDataSource {
+
+    private val sharedFlow = MutableSharedFlow<List<Stock>>()
+
+    suspend fun emit(stockList: List<Stock>) {
+        sharedFlow.emit(stockList)
+    }
+
+    override val latestStockList: Flow<List<Stock>> = sharedFlow.asSharedFlow()
+
+}

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase1/FlowUseCase1ViewModelTest.kt

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+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase1
+
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import com.lukaslechner.coroutineusecasesonandroid.utils.ReplaceMainDispatcherRule
+import junit.framework.Assert.assertEquals
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runTest
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TestRule
+
+class FlowUseCase1ViewModelTest {
+
+    @get:Rule
+    val testInstantTaskExecutorRule: TestRule = InstantTaskExecutorRule()
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    @get: Rule
+    val replaceMainDispatcherRule = ReplaceMainDispatcherRule()
+
+    private val receivedUiStates = mutableListOf<UiState>()
+
+    @Test
+    fun `should return success UI States with values of fakeDataSource`() = runTest {
+
+        val fakeDataSource = FakeStockPriceDataSource()
+        val viewModel = FlowUseCase1ViewModel(fakeDataSource)
+        observeViewModel(viewModel)
+
+        assertEquals(UiState.Loading, receivedUiStates[0])
+        assertEquals(1, receivedUiStates.size)
+
+        fakeDataSource.emit(listOf(googleStock, appleStock))
+        assertEquals(UiState.Success(listOf(googleStock, appleStock)), receivedUiStates[1])
+        assertEquals(2, receivedUiStates.size)
+
+        fakeDataSource.emit(listOf(googleStock))
+        assertEquals(UiState.Success(listOf(googleStock)), receivedUiStates[2])
+        assertEquals(3, receivedUiStates.size)
+    }
+
+    private fun observeViewModel(viewModel: FlowUseCase1ViewModel) {
+        viewModel.currentStockPriceAsLiveData.observeForever { uiState ->
+            if (uiState != null) {
+                receivedUiStates.add(uiState)
+            }
+        }
+    }
+}

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase1/TestData.kt

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+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase1
+
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.Stock
+
+val appleStock = Stock(
+    rank = 1,
+    name = "Apple",
+    symbol = "AAPL",
+    marketCap = 1.0f,
+    country = "United Stated",
+    currentPrice = 1.0f
+)
+
+val googleStock = Stock(
+    rank = 4,
+    name = "Alphabet",
+    symbol = "GOOG",
+    marketCap = 2.0f,
+    country = "United Stated",
+    currentPrice = 2.0f
+)