feat: view model testing and main dispatcher rule

Author: f-arslan

app/src/test/java/com/patika/getir_lite/ProductViewModelTest.kt

@@ -0,0 +1,104 @@
+package com.patika.getir_lite
+
+import com.patika.getir_lite.data.ProductRepository
+import com.patika.getir_lite.data.local.model.toProductWithCount
+import com.patika.getir_lite.fake.FakeProductDataSource
+import com.patika.getir_lite.model.BaseResponse
+import com.patika.getir_lite.model.ProductEvent
+import com.patika.getir_lite.util.MainDispatcherRule
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.advanceTimeBy
+import kotlinx.coroutines.test.advanceUntilIdle
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class ProductViewModelTest {
+
+    @get:Rule
+    val dispatcherRule = MainDispatcherRule()
+
+    private val repository: ProductRepository = FakeProductDataSource()
+    private lateinit var viewModel: ProductViewModel
+
+    @Before
+    fun setup() {
+        viewModel = ProductViewModel(repository)
+    }
+
+    @Test
+    fun `handle rapid consecutive product events correctly`() = runTest {
+        val addCount = 100
+        val minusCount = 49
+        repeat(addCount) {
+            viewModel.onEvent(ProductEvent.OnPlusClick(0L, it))
+            advanceTimeBy(200) // mock the real delay
+        }
+
+        repeat(minusCount) {
+            viewModel.onEvent(ProductEvent.OnMinusClick(0L, it))
+            advanceTimeBy(200)
+        }
+
+        val expectedCount = addCount - minusCount
+        val productResponse = viewModel.products.first()
+        if (productResponse is BaseResponse.Success) {
+            val pro = productResponse.data.find { it.productId == 0L }
+            assertEquals(expectedCount, pro?.count)
+        }
+    }
+
+    @Test
+    fun `handle high load of mixed operations gracefully`() = runTest {
+        val products = repository.getProductsAsFlow().first()
+        val suggestedProducts = repository.getSuggestedProductsAsFlow().first()
+
+        products.forEach {
+            repeat(100) { _ ->
+                viewModel.onEvent(ProductEvent.OnPlusClick(it.productId, 1))
+                advanceTimeBy(200)
+                viewModel.onEvent(ProductEvent.OnMinusClick(it.productId, 1))
+                advanceTimeBy(200)
+            }
+        }
+
+        suggestedProducts.forEach {
+            repeat(100) { _ ->
+                viewModel.onEvent(ProductEvent.OnPlusClick(it.productId, 1))
+                advanceTimeBy(200)
+                viewModel.onEvent(ProductEvent.OnMinusClick(it.productId, 1))
+                advanceTimeBy(200)
+            }
+        }
+
+        advanceUntilIdle()
+
+        val productResponse = viewModel.products.first()
+        val suggestedProductResponse = viewModel.suggestedProducts.first()
+        if (productResponse is BaseResponse.Success && suggestedProductResponse is BaseResponse.Success) {
+            val pro = productResponse.data.find { it.productId == 0L }
+            val suggestedPro = suggestedProductResponse.data.find { it.productId == 1L }
+            assertEquals(0, pro?.count)
+            assertEquals(0, suggestedPro?.count)
+        }
+    }
+
+    @Test
+    fun `update in product count reflects in basket with products`() = runTest {
+        val product = repository.getProductsAsFlow().first().first()
+        viewModel.onEvent(ProductEvent.OnPlusClick(product.productId))
+        advanceTimeBy(200)
+        advanceUntilIdle()
+        val basketResult = viewModel.basketWithProducts.first()
+        if (basketResult is BaseResponse.Success) {
+            val basket = basketResult.data
+            val item = basket.itemsWithProducts.map { it.toProductWithCount() }
+                .find { it.productId == product.productId }
+            assertEquals(1, item?.count)
+        }
+    }
+}

app/src/test/java/com/patika/getir_lite/util/MainDispatcherRule.kt

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+package com.patika.getir_lite.util
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class MainDispatcherRule(
+    private val testDispatcher: TestDispatcher = UnconfinedTestDispatcher()
+) : TestWatcher() {
+    override fun starting(description: Description?) = Dispatchers.setMain(testDispatcher)
+    override fun finished(description: Description?) = Dispatchers.resetMain()
+}