HomeScreenTests.kt

/*
 * Copyright 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.jetnews

import androidx.compose.foundation.lazy.rememberLazyListState
import androidx.compose.material3.SnackbarHostState
import androidx.compose.runtime.snapshotFlow
import androidx.compose.ui.test.junit4.v2.createComposeRule
import androidx.test.ext.junit.runners.AndroidJUnit4
import androidx.test.platform.app.InstrumentationRegistry
import com.example.jetnews.ui.home.HomeFeedScreen
import com.example.jetnews.ui.home.HomeUiState
import com.example.jetnews.ui.theme.JetnewsTheme
import com.example.jetnews.utils.ErrorMessage
import kotlinx.coroutines.flow.filterNotNull
import kotlinx.coroutines.flow.first
import kotlinx.coroutines.runBlocking
import org.junit.Assert.assertEquals
import org.junit.Rule
import org.junit.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class HomeScreenTests {

    @get:Rule
    val composeTestRule = createComposeRule()

    /**
     * Checks that the Snackbar is shown when the HomeScreen data contains an error.
     */
    @Test
    fun postsContainError_snackbarShown() {
        val snackbarHostState = SnackbarHostState()
        composeTestRule.setContent {
            JetnewsTheme {

                // When the Home screen receives data with an error
                HomeFeedScreen(
                    uiState = HomeUiState.NoPosts(
                        isLoading = false,
                        errorMessages = listOf(ErrorMessage(0L, R.string.load_error)),
                        searchInput = "",
                    ),
                    showTopAppBar = false,
                    onToggleFavorite = {},
                    onSelectPost = {},
                    onRefreshPosts = {},
                    onErrorDismiss = {},
                    openDrawer = {},
                    homeListLazyListState = rememberLazyListState(),
                    snackbarHostState = snackbarHostState,
                    onSearchInputChanged = {},
                )
            }
        }

        // Then the first message received in the Snackbar is an error message
        runBlocking {
            // snapshotFlow converts a State to a Kotlin Flow so we can observe it
            // wait for the first a non-null `currentSnackbarData`
            val actualSnackbarText = snapshotFlow { snackbarHostState.currentSnackbarData }
                .filterNotNull().first().visuals.message
            val expectedSnackbarText = InstrumentationRegistry.getInstrumentation()
                .targetContext.resources.getString(R.string.load_error)
            assertEquals(expectedSnackbarText, actualSnackbarText)
        }
    }
}