tests: add unit tests for MainActivityViewModel

Author: superus8r

app/src/test/java/org/kabiri/android/usbterminal/viewmodel/MainActivityViewModelTest.kt

@@ -0,0 +1,65 @@
+package org.kabiri.android.usbterminal.viewmodel
+
+import com.google.common.truth.Truth.assertThat
+import io.mockk.clearAllMocks
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.unmockkStatic
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.kabiri.android.usbterminal.R
+import org.kabiri.android.usbterminal.domain.IArduinoUseCase
+import org.kabiri.android.usbterminal.domain.IUsbUseCase
+import org.kabiri.android.usbterminal.util.IResourceProvider
+
+@OptIn(ExperimentalCoroutinesApi::class)
+internal class MainActivityViewModelTest {
+
+    private val testDispatcher: TestDispatcher = StandardTestDispatcher()
+    private val testScope = TestScope(testDispatcher)
+
+    val mockArduinoUsecase: IArduinoUseCase = mockk(relaxed = true)
+    val mockUsbUseCase: IUsbUseCase = mockk(relaxed = true)
+    val mockResourceProvider: IResourceProvider = mockk(relaxed = true)
+
+    private lateinit var sut: MainActivityViewModel
+
+    @Before
+    fun setUp() {
+        Dispatchers.setMain(testDispatcher)
+        sut = MainActivityViewModel(
+            arduinoUseCase = mockArduinoUsecase,
+            usbUseCase = mockUsbUseCase,
+            resourceProvider = mockResourceProvider,
+        )
+    }
+
+    @After
+    fun cleanUp() {
+        Dispatchers.resetMain()
+        unmockkStatic("org.kabiri.android.usbterminal.util.UsbDeviceExtensionsKt")
+        clearAllMocks()
+    }
+
+    @Test
+    fun `connect emits expected message when device list is empty`() {
+        // arrange
+        val expected = "this is an error"
+        every { mockUsbUseCase.scanForUsbDevices() } returns emptyList()
+        every { mockResourceProvider.getString(R.string.helper_error_usb_devices_not_attached) } returns expected
+
+        // act
+        sut.connect()
+
+        // assert
+        assertThat(sut.errorMessage.value).isEqualTo(expected)
+    }
+}