[Add] NavigatorTest

Author: jeprubio

app/src/test/java/com/rumosoft/marvelcompose/presentation/navigation/NavigatorTest.kt

@@ -0,0 +1,121 @@
+package com.rumosoft.marvelcompose.presentation.navigation
+
+import androidx.compose.runtime.mutableStateOf
+import androidx.navigation3.runtime.NavBackStack
+import androidx.navigation3.runtime.NavKey
+import com.rumosoft.components.presentation.deeplinks.CharacterDetails
+import com.rumosoft.components.presentation.deeplinks.CharactersScreen
+import com.rumosoft.components.presentation.deeplinks.ComicDetails
+import com.rumosoft.components.presentation.deeplinks.ComicsScreen
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+class NavigatorTest {
+
+    private lateinit var navigator: Navigator
+    private lateinit var state: NavigationState
+
+    @BeforeEach
+    fun setUp() {
+        val charactersStack = NavBackStack<NavKey>(CharactersScreen)
+        val comicsStack = NavBackStack<NavKey>(ComicsScreen)
+        state = NavigationState(
+            startRoute = CharactersScreen,
+            topLevelRoute = mutableStateOf(CharactersScreen),
+            backStacks = mapOf(
+                CharactersScreen to charactersStack,
+                ComicsScreen to comicsStack,
+            ),
+        )
+        navigator = Navigator(state)
+    }
+
+    @Test
+    fun `navigate to top-level route switches tab`() {
+        navigator.navigate(ComicsScreen)
+
+        assertEquals(ComicsScreen, state.topLevelRoute)
+    }
+
+    @Test
+    fun `navigate to detail route pushes onto current stack`() {
+        val detail = CharacterDetails(42L)
+
+        navigator.navigate(detail)
+
+        val stack = state.backStacks[CharactersScreen]!!
+        assertEquals(listOf(CharactersScreen, detail), stack.toList())
+    }
+
+    @Test
+    fun `navigateOnTab switches tab and pushes route`() {
+        val comicDetail = ComicDetails(123)
+
+        navigator.navigateOnTab(ComicsScreen, comicDetail)
+
+        assertEquals(ComicsScreen, state.topLevelRoute)
+        val stack = state.backStacks[ComicsScreen]!!
+        assertEquals(listOf(ComicsScreen, comicDetail), stack.toList())
+    }
+
+    @Test
+    fun `goBack pops current entry from stack`() {
+        navigator.navigate(CharacterDetails(1L))
+
+        navigator.goBack()
+
+        val stack = state.backStacks[CharactersScreen]!!
+        assertEquals(listOf<NavKey>(CharactersScreen), stack.toList())
+    }
+
+    @Test
+    fun `goBack at base of non-start tab returns to start tab`() {
+        navigator.navigate(ComicsScreen)
+        assertEquals(ComicsScreen, state.topLevelRoute)
+
+        navigator.goBack()
+
+        assertEquals(CharactersScreen, state.topLevelRoute)
+    }
+
+    @Test
+    fun `switchTabAndNavigate pops current entry and navigates to target tab`() {
+        // Simulate being on a character details screen
+        navigator.navigate(CharacterDetails(1L))
+        assertEquals(
+            listOf<NavKey>(CharactersScreen, CharacterDetails(1L)),
+            state.backStacks[CharactersScreen]!!.toList(),
+        )
+
+        // Switch to comics tab with a comic detail
+        val comicDetail = ComicDetails(99)
+        navigator.switchTabAndNavigate(ComicsScreen, comicDetail)
+
+        // Current entry popped from characters stack
+        assertEquals(
+            listOf<NavKey>(CharactersScreen),
+            state.backStacks[CharactersScreen]!!.toList(),
+        )
+        // Switched to comics tab
+        assertEquals(ComicsScreen, state.topLevelRoute)
+        // Comic detail pushed onto comics stack
+        assertEquals(
+            listOf<NavKey>(ComicsScreen, comicDetail),
+            state.backStacks[ComicsScreen]!!.toList(),
+        )
+    }
+
+    @Test
+    fun `stacksInUse returns only start route when on start tab`() {
+        assertEquals(listOf<NavKey>(CharactersScreen), state.stacksInUse)
+    }
+
+    @Test
+    fun `stacksInUse returns start and current when on different tab`() {
+        navigator.navigate(ComicsScreen)
+
+        assertEquals(listOf<NavKey>(CharactersScreen, ComicsScreen), state.stacksInUse)
+    }
+}
+