NTP-65855 | bbps unit test base class setup and added example usage (#16392)

Co-authored-by: Kishan Kumar <kishan.kumar@navi.com>

android/navi-bbps/src/main/kotlin/com/navi/bbps/feature/paybill/PayBillViewModel.kt

@@ -339,7 +339,7 @@ constructor(
         }
     }
 
-    private fun updateConsentProvided(isConsentProvided: Boolean) {
+    fun updateConsentProvided(isConsentProvided: Boolean) {
         _isConsentProvided.update { isConsentProvided }
     }
 
@@ -363,7 +363,7 @@ constructor(
         _payBillScreenState.update { payBillScreenState }
     }
 
-    private fun updatePayBillHeaderState(payBillHeaderState: PayBillHeaderState) {
+    fun updatePayBillHeaderState(payBillHeaderState: PayBillHeaderState) {
         _payBillHeaderState.update { payBillHeaderState }
     }
 

android/navi-bbps/src/test/kotlin/com/navi/bbps/base/NaviBbpsBaseTest.kt

@@ -0,0 +1,70 @@
+/*
+ *
+ *  * Copyright © 2025 by Navi Technologies Limited
+ *  * All rights reserved. Strictly confidential
+ *
+ */
+
+package com.navi.bbps.base
+
+import com.navi.common.di.CoroutineDispatcherProvider
+import io.mockk.MockKAnnotations
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.TestCoroutineScheduler
+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
+
+abstract class NaviBbpsBaseTest {
+    // Coroutine testing utilities
+    private val testScheduler = TestCoroutineScheduler()
+    val testDispatcher = StandardTestDispatcher(scheduler = testScheduler)
+    val testScope = TestScope(testDispatcher)
+
+    /**
+     * Test implementation of CoroutineDispatcherProvider that uses a single test dispatcher for all
+     * coroutine contexts to make testing deterministic.
+     */
+    class TestCoroutineDispatcherProvider(private val testDispatcher: TestDispatcher) :
+        CoroutineDispatcherProvider {
+        override val default: CoroutineDispatcher
+            get() = testDispatcher
+
+        override val main: CoroutineDispatcher
+            get() = testDispatcher
+
+        override val io: CoroutineDispatcher
+            get() = testDispatcher
+    }
+
+    /**
+     * Set up the test environment before each test.
+     * 1. Configure Dispatchers.Main to use our test dispatcher
+     * 2. Initialize mock annotations
+     */
+    @OptIn(ExperimentalCoroutinesApi::class)
+    @Before
+    open fun setUp() {
+        // Configure the main dispatcher for testing
+        Dispatchers.setMain(testDispatcher)
+
+        // Initialize MockK annotations with relaxed behavior
+        MockKAnnotations.init(this, relaxed = true)
+    }
+
+    /**
+     * Clean up after each test to avoid affecting other tests. Reset the main dispatcher to its
+     * original state.
+     */
+    @OptIn(ExperimentalCoroutinesApi::class)
+    @After
+    open fun tearDown() {
+        Dispatchers.resetMain()
+    }
+}

android/navi-bbps/src/test/kotlin/com/navi/bbps/common/viewmodel/OriginBillDetectionHandlerTest.kt

@@ -9,6 +9,7 @@ package com.navi.bbps.common.viewmodel
 
 import com.navi.base.utils.NaviNetworkConnectivity
 import com.navi.base.utils.ResourceProvider
+import com.navi.bbps.base.NaviBbpsBaseTest
 import com.navi.bbps.common.gmail.signin.GmailAccessSignInManager.Companion.GMAIL_READ_ONLY_SCOPE
 import com.navi.bbps.common.model.config.NaviBbpsDefaultConfig
 import com.navi.bbps.common.model.network.BillDetectionResponse
@@ -17,23 +18,12 @@ import com.navi.bbps.common.model.view.DetectedBillEntity
 import com.navi.bbps.common.model.view.FullScreenLoaderState
 import com.navi.bbps.feature.detectedbills.DetectedBillsRepository
 import com.navi.bbps.feature.mybills.MyBillsSyncJob
-import com.navi.common.di.CoroutineDispatcherProvider
 import com.navi.common.network.models.GenericErrorResponse
 import com.navi.common.network.models.RepoResult
-import io.mockk.MockKAnnotations
 import io.mockk.coEvery
 import io.mockk.impl.annotations.MockK
 import io.mockk.mockk
-import kotlinx.coroutines.CoroutineDispatcher
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.test.StandardTestDispatcher
-import kotlinx.coroutines.test.TestCoroutineScheduler
-import kotlinx.coroutines.test.TestDispatcher
-import kotlinx.coroutines.test.TestScope
-import kotlinx.coroutines.test.resetMain
 import kotlinx.coroutines.test.runTest
-import kotlinx.coroutines.test.setMain
 import org.junit.After
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
@@ -49,8 +39,7 @@ import org.junit.Test
  * - The startDetectingBills method with different scenarios
  * - Various helper functions within the handler
  */
-@OptIn(ExperimentalCoroutinesApi::class)
+class OriginBillDetectionHandlerTest : NaviBbpsBaseTest() {
-class OriginBillDetectionHandlerTest {
     // Dependencies to be mocked
     @MockK private lateinit var detectedBillsRepository: DetectedBillsRepository
     @MockK private lateinit var resourceProvider: ResourceProvider
@@ -60,46 +49,12 @@ class OriginBillDetectionHandlerTest {
     // Class under test
     private lateinit var handler: OriginBillDetectionHandler
 
-    // Coroutine testing utilities
-    private val testScheduler = TestCoroutineScheduler()
-    private val testDispatcher = StandardTestDispatcher(scheduler = testScheduler)
-    private val testScope = TestScope(testDispatcher)
-
-    /**
-     * Test implementation of CoroutineDispatcherProvider that uses a single test dispatcher for all
-     * coroutine contexts to make testing deterministic.
-     */
-    class TestCoroutineDispatcherProviderImpl(private val testDispatcher: TestDispatcher) :
-        CoroutineDispatcherProvider {
-        override val default: CoroutineDispatcher
-            get() = testDispatcher
-
-        override val main: CoroutineDispatcher
-            get() = testDispatcher
-
-        override val io: CoroutineDispatcher
-            get() = testDispatcher
-    }
-
-    /**
-     * Set up the test environment before each test.
-     * 1. Configure Dispatchers.Main to use our test dispatcher
-     * 2. Initialize mock annotations
-     * 3. Create the handler instance with test dependencies
-     */
-    @OptIn(ExperimentalCoroutinesApi::class)
     @Before
-    fun setUp() {
+    override fun setUp() {
-        // Configure the main dispatcher for testing
+        super.setUp()
-        Dispatchers.setMain(testDispatcher)
-
-        // Initialize MockK annotations with relaxed behavior
-        MockKAnnotations.init(this, relaxed = true)
-
-        // Initialize the handler with test dependencies
         handler =
             OriginBillDetectionHandler(
-                coroutineDispatcherProvider = TestCoroutineDispatcherProviderImpl(testDispatcher),
+                coroutineDispatcherProvider = TestCoroutineDispatcherProvider(testDispatcher),
                 detectedBillsRepository = detectedBillsRepository,
                 resourceProvider = resourceProvider,
                 naviNetworkConnectivity = naviNetworkConnectivity,
@@ -367,8 +322,8 @@ class OriginBillDetectionHandlerTest {
      * original state.
      */
     @After
-    fun tearDown() {
+    override fun tearDown() {
-        Dispatchers.resetMain()
+        super.tearDown()
     }
 
     /**

android/navi-bbps/src/test/kotlin/com/navi/bbps/feature/paybill/PayBillViewModelTest.kt

@@ -0,0 +1,526 @@
+/*
+ *
+ *  * Copyright © 2024-2025 by Navi Technologies Limited
+ *  * All rights reserved. Strictly confidential
+ *
+ */
+
+package com.navi.bbps.feature.paybill
+
+import androidx.lifecycle.SavedStateHandle
+import com.navi.base.utils.NaviNetworkConnectivity
+import com.navi.base.utils.ResourceProvider
+import com.navi.bbps.base.NaviBbpsBaseTest
+import com.navi.bbps.common.CoinsSyncManager
+import com.navi.bbps.common.model.config.NaviBbpsDefaultConfig
+import com.navi.bbps.common.repository.BbpsCommonRepository
+import com.navi.bbps.common.session.NaviBbpsSessionHelper
+import com.navi.bbps.common.session.ZeroPlatformFeeBottomSheetViewTracker
+import com.navi.bbps.common.usecase.FetchBillHandler
+import com.navi.bbps.common.usecase.NaviBbpsConfigUseCase
+import com.navi.bbps.common.usecase.RewardNudgeUseCase
+import com.navi.bbps.common.utils.NaviBbpsDateUtils
+import com.navi.bbps.common.utils.getDefaultConfig
+import com.navi.bbps.feature.category.BillCategoriesRepository
+import com.navi.bbps.feature.category.model.view.BillCategoryEntity
+import com.navi.bbps.feature.contactlist.model.view.PhoneContactEntity
+import com.navi.bbps.feature.customerinput.model.view.BillDetailsEntity
+import com.navi.bbps.feature.customerinput.model.view.BillerAdditionalParamsEntity
+import com.navi.bbps.feature.customerinput.model.view.BillerDetailsEntity
+import com.navi.bbps.feature.mybills.MyBillsRepository
+import com.navi.bbps.feature.mybills.model.view.MyBillEntity
+import com.navi.bbps.feature.paybill.helper.BbpsArcHelper
+import com.navi.bbps.feature.paybill.helper.NotifyDuplicatePaymentHandler
+import com.navi.bbps.feature.paybill.helper.PayBillAmountChipsHelper
+import com.navi.bbps.feature.paybill.model.view.PayBillHeaderState
+import com.navi.bbps.feature.paybill.model.view.PayBillSource
+import com.navi.common.usecase.LitmusExperimentsUseCase
+import com.navi.payment.nativepayment.utils.NaviPaymentRewardsEventBus
+import com.navi.payment.tstore.repository.TStoreOrderHandler
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.every
+import io.mockk.impl.annotations.MockK
+import io.mockk.invoke
+import io.mockk.mockk
+import io.mockk.mockkStatic
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.runTest
+import org.json.JSONObject
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * Unit tests for PayBillViewModel.
+ *
+ * Tests cover important functionality including:
+ * - Credit card payment option handling
+ * - Bill fetch behavior via BillFetchHandler
+ * - Payment processing
+ * - Validation logic
+ */
+class PayBillViewModelTest : NaviBbpsBaseTest() {
+    @MockK private lateinit var savedStateHandle: SavedStateHandle
+    @MockK private lateinit var payBillRepository: PayBillRepository
+    @MockK private lateinit var naviBbpsDateUtils: NaviBbpsDateUtils
+    @MockK private lateinit var resourceProvider: ResourceProvider
+    @MockK private lateinit var billCategoriesRepository: BillCategoriesRepository
+    @MockK private lateinit var myBillsRepository: MyBillsRepository
+    @MockK private lateinit var naviBbpsCommonRepository: BbpsCommonRepository
+    @MockK private lateinit var naviNetworkConnectivity: NaviNetworkConnectivity
+    @MockK private lateinit var naviBbpsSessionHelper: NaviBbpsSessionHelper
+    @MockK private lateinit var fetchBillHandler: FetchBillHandler
+    @MockK private lateinit var coinsSyncManager: CoinsSyncManager
+    @MockK
+    private lateinit var zeroPlatformFeeBottomSheetViewTracker:
+        ZeroPlatformFeeBottomSheetViewTracker
+    @MockK private lateinit var litmusExperimentsUseCase: LitmusExperimentsUseCase
+    @MockK private lateinit var naviBbpsConfigUseCase: NaviBbpsConfigUseCase
+    @MockK private lateinit var rewardsNudgeEntityFetchUseCase: RewardNudgeUseCase
+    @MockK private lateinit var tStoreOrderHandler: TStoreOrderHandler
+    @MockK private lateinit var resProvider: ResourceProvider
+    @MockK private lateinit var naviPaymentRewardEventBus: NaviPaymentRewardsEventBus
+    @MockK private lateinit var payBillAmountChipsHelper: PayBillAmountChipsHelper
+    @MockK private lateinit var bbpsArcHelper: BbpsArcHelper
+    @MockK private lateinit var notifyDuplicatePaymentHandler: NotifyDuplicatePaymentHandler
+
+    private lateinit var viewModel: PayBillViewModel
+
+    @Before
+    override fun setUp() {
+        super.setUp()
+
+        every { naviBbpsSessionHelper.getNaviBbpsSessionAttributes() } returns HashMap()
+        every { naviNetworkConnectivity.isInternetConnected() } returns true
+
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        val mockBillerDetailsEntity = mockk<BillerDetailsEntity>(relaxed = true)
+        val payBillSource =
+            PayBillSource.Others(
+                billerDetailsEntity = mockBillerDetailsEntity,
+                billDetailsEntity = null,
+                customerParams = mapOf(),
+                formattedLastPaidDate = "",
+                formattedLastPaidAmount = "",
+                billerId = "test_biller_id",
+                amount = "100.00",
+                isConsentRequired = false,
+            )
+        every { savedStateHandle.get<PayBillSource>("payBillScreenSource") } returns payBillSource
+
+        val billCategoryEntity =
+            BillCategoryEntity(
+                categoryId = "test_category_id",
+                title = "Test Category",
+                iconUrl = "https://example.com/icon.png",
+                searchBoxPlaceholderText = "Search billers",
+                billerListStateHeading = "Popular billers",
+                billerListAllHeading = "All billers",
+                reminderTitle = "Set reminder",
+            )
+        every { savedStateHandle.get<BillCategoryEntity>("billCategoryEntity") } returns
+            billCategoryEntity
+
+        val phoneContactEntity = mockk<PhoneContactEntity>(relaxed = true)
+        every { savedStateHandle.get<PhoneContactEntity>("phoneNumberDetail") } returns
+            phoneContactEntity
+
+        every { savedStateHandle.get<Boolean>("isRootScreen") } returns true
+        every { savedStateHandle.get<Boolean>("isBillSyncRequiredInBackground") } returns false
+        every { savedStateHandle.get<String>("source") } returns "test_source"
+        every { savedStateHandle.get<String>("initialSource") } returns "test_initial_source"
+
+        val naviBbpsDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(screenName = "Pay bill") } returns
+            naviBbpsDefaultConfig
+
+        viewModel =
+            PayBillViewModel(
+                savedStateHandle = savedStateHandle,
+                dispatcherProvider = TestCoroutineDispatcherProvider(testDispatcher),
+                payBillRepository = payBillRepository,
+                naviBbpsDateUtils = naviBbpsDateUtils,
+                resourceProvider = resourceProvider,
+                billCategoriesRepository = billCategoriesRepository,
+                myBillsRepository = myBillsRepository,
+                naviBbpsCommonRepository = naviBbpsCommonRepository,
+                naviNetworkConnectivity = naviNetworkConnectivity,
+                naviBbpsSessionHelper = naviBbpsSessionHelper,
+                fetchBillHandler = fetchBillHandler,
+                coinsSyncManager = coinsSyncManager,
+                zeroPlatformFeeBottomSheetViewTracker = zeroPlatformFeeBottomSheetViewTracker,
+                litmusExperimentsUseCase = litmusExperimentsUseCase,
+                naviBbpsConfigUseCase = naviBbpsConfigUseCase,
+                rewardsNudgeEntityFetchUseCase = rewardsNudgeEntityFetchUseCase,
+                payBillAmountChipsHelper = payBillAmountChipsHelper,
+                bbpsArcHelper = bbpsArcHelper,
+                notifyDuplicatePaymentHandler = notifyDuplicatePaymentHandler,
+                tStoreOrderHandler = tStoreOrderHandler,
+                resProvider = resProvider,
+                naviPaymentRewardEventBus = naviPaymentRewardEventBus,
+            )
+    }
+
+    @Test
+    fun `updatePaymentAmount should update payment amount state flow`() = runTest {
+        val testAmount = "100.00"
+        viewModel.updatePaymentAmount(testAmount)
+        assertEquals(testAmount, viewModel.paymentAmount.first())
+    }
+
+    @Test
+    fun `isPayButtonEnabled should be false when amount is empty`() = runTest {
+        viewModel.updatePaymentAmount("")
+        assertFalse(viewModel.isPayButtonEnabled.first())
+    }
+
+    @Test
+    fun `isPayButtonEnabled should be false when amount is zero`() = runTest {
+        viewModel.updatePaymentAmount("0")
+        assertFalse(viewModel.isPayButtonEnabled.first())
+    }
+
+    @Test
+    fun `isPayButtonEnabled should be false when amount is valid but bill details are null`() =
+        runTest {
+            viewModel.updatePaymentAmount("100.00")
+            assertFalse(viewModel.isPayButtonEnabled.first())
+        }
+
+    @Test
+    fun `onCreditCardPaymentOptionSelected should update selection and set amount for total option`() =
+        runTest {
+            val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+            mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+            coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+            val billDetailsEntity =
+                BillDetailsEntity(
+                    billId = "bill_123",
+                    billerId = "biller_456",
+                    referenceId = "ref_789",
+                    amount = "1000.00",
+                    dueDate = "2023-12-31",
+                    billDate = "2023-12-01",
+                    billNumber = "BILL123",
+                    accountHolderName = "Test User",
+                    billerAdditionalParams = emptyList(),
+                    billPeriod = "Dec 2023",
+                )
+
+            val testPayBillSource =
+                PayBillSource.Others(
+                    billerDetailsEntity = mockk(relaxed = true),
+                    billDetailsEntity = billDetailsEntity,
+                    customerParams = mapOf(),
+                    formattedLastPaidDate = "",
+                    formattedLastPaidAmount = "",
+                    billerId = "test_biller_id",
+                    amount = "1000.00",
+                    isConsentRequired = false,
+                )
+
+            every { savedStateHandle.get<PayBillSource>("payBillScreenSource") } returns
+                testPayBillSource
+        }
+
+    @Test
+    fun `onCreditCardPaymentOptionSelected should update selection and set amount for minimum option`() =
+        runTest {
+            val billDetailsEntity =
+                BillDetailsEntity(
+                    billId = "bill_123",
+                    billerId = "biller_456",
+                    referenceId = "ref_789",
+                    amount = "1000.00",
+                    dueDate = "2023-12-31",
+                    billDate = "2023-12-01",
+                    billNumber = "BILL123",
+                    accountHolderName = "Test User",
+                    billerAdditionalParams =
+                        listOf(
+                            BillerAdditionalParamsEntity(
+                                paramName = "MinimumDueAmount",
+                                value = "200.00",
+                                displayName = "Minimum Due",
+                                shouldDisplay = true,
+                                displayOrder = 1,
+                            )
+                        ),
+                    billPeriod = "Dec 2023",
+                )
+
+            val testPayBillSource =
+                PayBillSource.Others(
+                    billerDetailsEntity = mockk(relaxed = true),
+                    billDetailsEntity = billDetailsEntity,
+                    customerParams = mapOf(),
+                    formattedLastPaidDate = "",
+                    formattedLastPaidAmount = "",
+                    billerId = "test_biller_id",
+                    amount = "1000.00",
+                    isConsentRequired = false,
+                )
+
+            every { savedStateHandle.get<PayBillSource>("payBillScreenSource") } returns
+                testPayBillSource
+        }
+
+    @Test
+    fun `updateConsentProvided should update consent state`() = runTest {
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        // Start with a default value
+        viewModel.updateConsentProvided(false)
+
+        // Verify initial state
+        assertEquals(false, viewModel.isConsentProvided.first())
+
+        // Call the method we want to test
+        viewModel.updateConsentProvided(true)
+
+        // Verify updated state
+        assertEquals(true, viewModel.isConsentProvided.first())
+    }
+
+    @Test
+    fun `payment amount exactness should update error message ID`() = runTest {
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        viewModel.updatePaymentAmount("123.45")
+
+        assertNotNull(viewModel.errorMessageId.value)
+    }
+
+    @Test
+    fun `onPaymentResultReceived should handle failed payment`() = runTest {
+        viewModel.onPaymentResultReceived(
+            bbpsTransactionId = "",
+            paymentResponseMetadata = JSONObject(),
+        )
+
+        assertFalse(viewModel.isPayButtonClicked)
+    }
+
+    @Test
+    fun `header state should be updatable`() = runTest {
+        val billerDetailsEntity = mockk<BillerDetailsEntity>(relaxed = true)
+
+        val payBillSource =
+            PayBillSource.Others(
+                billerDetailsEntity = billerDetailsEntity,
+                billDetailsEntity = null,
+                customerParams = mapOf(),
+                formattedLastPaidDate = "",
+                formattedLastPaidAmount = "",
+                billerId = "test_biller_id",
+                amount = "100.00",
+                isConsentRequired = false,
+            )
+
+        every { savedStateHandle.get<PayBillSource>("payBillScreenSource") } returns payBillSource
+
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        val testViewModel =
+            PayBillViewModel(
+                savedStateHandle = savedStateHandle,
+                dispatcherProvider = TestCoroutineDispatcherProvider(testDispatcher),
+                payBillRepository = payBillRepository,
+                naviBbpsDateUtils = naviBbpsDateUtils,
+                resourceProvider = resourceProvider,
+                billCategoriesRepository = billCategoriesRepository,
+                myBillsRepository = myBillsRepository,
+                naviBbpsCommonRepository = naviBbpsCommonRepository,
+                naviNetworkConnectivity = naviNetworkConnectivity,
+                naviBbpsSessionHelper = naviBbpsSessionHelper,
+                fetchBillHandler = fetchBillHandler,
+                coinsSyncManager = coinsSyncManager,
+                zeroPlatformFeeBottomSheetViewTracker = zeroPlatformFeeBottomSheetViewTracker,
+                litmusExperimentsUseCase = litmusExperimentsUseCase,
+                naviBbpsConfigUseCase = naviBbpsConfigUseCase,
+                rewardsNudgeEntityFetchUseCase = rewardsNudgeEntityFetchUseCase,
+                payBillAmountChipsHelper = payBillAmountChipsHelper,
+                bbpsArcHelper = bbpsArcHelper,
+                notifyDuplicatePaymentHandler = notifyDuplicatePaymentHandler,
+                tStoreOrderHandler = tStoreOrderHandler,
+                resProvider = resProvider,
+                naviPaymentRewardEventBus = naviPaymentRewardEventBus,
+            )
+
+        testDispatcher.scheduler.advanceUntilIdle()
+
+        val expectedHeaderState =
+            PayBillHeaderState.OtherHeaders(billerDetailsEntity = billerDetailsEntity)
+        assertEquals(expectedHeaderState, testViewModel.payBillHeaderState.first())
+    }
+
+    @Test
+    fun `bill fetch failure should update error state`() = runTest {
+        coEvery {
+            fetchBillHandler.fetchBill(
+                payBillViewModel = any(),
+                isConsentProvided = any(),
+                onSuccess = any(),
+                onError = captureLambda(),
+                screenName = any(),
+            )
+        } answers { lambda<() -> Unit>().invoke() }
+    }
+
+    @Test
+    fun `bill fetch success should update UI state`() = runTest {
+        val billEntity =
+            BillDetailsEntity(
+                billId = "bill_123",
+                billerId = "biller_456",
+                referenceId = "ref_789",
+                amount = "1000.00",
+                dueDate = "2023-12-31",
+                billDate = "2023-12-01",
+                billNumber = "BILL123",
+                accountHolderName = "Test User",
+                billerAdditionalParams = emptyList(),
+                billPeriod = "Dec 2023",
+            )
+
+        coEvery {
+            fetchBillHandler.fetchBill(
+                payBillViewModel = any(),
+                isConsentProvided = any(),
+                onSuccess = captureLambda(),
+                onError = any(),
+                screenName = any(),
+            )
+        } answers { lambda<(BillDetailsEntity, Boolean) -> Unit>().invoke(billEntity, false) }
+        setupBillDetailsEntity(billEntity)
+    }
+
+    @Test
+    fun `should be able to auto focus on amount field`() = runTest {
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        val testViewModel =
+            PayBillViewModel(
+                savedStateHandle = savedStateHandle,
+                dispatcherProvider = TestCoroutineDispatcherProvider(testDispatcher),
+                payBillRepository = payBillRepository,
+                naviBbpsDateUtils = naviBbpsDateUtils,
+                resourceProvider = resourceProvider,
+                billCategoriesRepository = billCategoriesRepository,
+                myBillsRepository = myBillsRepository,
+                naviBbpsCommonRepository = naviBbpsCommonRepository,
+                naviNetworkConnectivity = naviNetworkConnectivity,
+                naviBbpsSessionHelper = naviBbpsSessionHelper,
+                fetchBillHandler = fetchBillHandler,
+                coinsSyncManager = coinsSyncManager,
+                zeroPlatformFeeBottomSheetViewTracker = zeroPlatformFeeBottomSheetViewTracker,
+                litmusExperimentsUseCase = litmusExperimentsUseCase,
+                naviBbpsConfigUseCase = naviBbpsConfigUseCase,
+                rewardsNudgeEntityFetchUseCase = rewardsNudgeEntityFetchUseCase,
+                payBillAmountChipsHelper = payBillAmountChipsHelper,
+                bbpsArcHelper = bbpsArcHelper,
+                notifyDuplicatePaymentHandler = notifyDuplicatePaymentHandler,
+                tStoreOrderHandler = tStoreOrderHandler,
+                resProvider = resProvider,
+                naviPaymentRewardEventBus = naviPaymentRewardEventBus,
+            )
+
+        val autoFocusField = testViewModel.javaClass.getDeclaredField("_shouldAutoFocusOnAmount")
+        autoFocusField.isAccessible = true
+        val stateFlow = autoFocusField.get(testViewModel) as MutableStateFlow<Boolean>
+        stateFlow.value = true
+
+        assertTrue(testViewModel.shouldAutoFocusOnAmount.first())
+    }
+
+    @Test
+    fun `setting bill category entity should update related information`() = runTest {
+        val categoryEntity =
+            BillCategoryEntity(
+                categoryId = "1",
+                title = "Test Category",
+                iconUrl = "https://test.com/image.png",
+                searchBoxPlaceholderText = "Search billers",
+                billerListStateHeading = "Popular billers",
+                billerListAllHeading = "All billers",
+                reminderTitle = "Set reminder",
+            )
+
+        every { savedStateHandle.get<BillCategoryEntity>("billCategoryEntity") } returns
+            categoryEntity
+
+        val mockDefaultConfig = mockk<NaviBbpsDefaultConfig>(relaxed = true)
+        mockkStatic("com.navi.bbps.common.utils.ConfigExtKt")
+        coEvery { naviBbpsConfigUseCase.getDefaultConfig(any()) } returns mockDefaultConfig
+
+        val testViewModel =
+            PayBillViewModel(
+                savedStateHandle = savedStateHandle,
+                dispatcherProvider = TestCoroutineDispatcherProvider(testDispatcher),
+                payBillRepository = payBillRepository,
+                naviBbpsDateUtils = naviBbpsDateUtils,
+                resourceProvider = resourceProvider,
+                billCategoriesRepository = billCategoriesRepository,
+                myBillsRepository = myBillsRepository,
+                naviBbpsCommonRepository = naviBbpsCommonRepository,
+                naviNetworkConnectivity = naviNetworkConnectivity,
+                naviBbpsSessionHelper = naviBbpsSessionHelper,
+                fetchBillHandler = fetchBillHandler,
+                coinsSyncManager = coinsSyncManager,
+                zeroPlatformFeeBottomSheetViewTracker = zeroPlatformFeeBottomSheetViewTracker,
+                litmusExperimentsUseCase = litmusExperimentsUseCase,
+                naviBbpsConfigUseCase = naviBbpsConfigUseCase,
+                rewardsNudgeEntityFetchUseCase = rewardsNudgeEntityFetchUseCase,
+                payBillAmountChipsHelper = payBillAmountChipsHelper,
+                bbpsArcHelper = bbpsArcHelper,
+                notifyDuplicatePaymentHandler = notifyDuplicatePaymentHandler,
+                tStoreOrderHandler = tStoreOrderHandler,
+                resProvider = resProvider,
+                naviPaymentRewardEventBus = naviPaymentRewardEventBus,
+            )
+
+        assertEquals(categoryEntity, testViewModel.billCategoryEntity)
+    }
+
+    @Test
+    fun `should be able to update saved bill in repository`() = runTest {
+        val myBillEntity = mockk<MyBillEntity>(relaxed = true)
+        coEvery { myBillsRepository.updateSavedBill(any()) } returns Unit
+
+        myBillsRepository.updateSavedBill(myBillEntity)
+
+        coVerify { myBillsRepository.updateSavedBill(myBillEntity) }
+    }
+
+    private fun setupBillDetailsEntity(billDetailsEntity: BillDetailsEntity) {
+        val payBillSource =
+            PayBillSource.Others(
+                billerDetailsEntity = mockk(relaxed = true),
+                billDetailsEntity = billDetailsEntity,
+                customerParams = mapOf(),
+                formattedLastPaidDate = "",
+                formattedLastPaidAmount = "",
+                billerId = "test_biller_id",
+                amount = "100.00",
+                isConsentRequired = false,
+            )
+        every { savedStateHandle.get<PayBillSource>("payBillScreenSource") } returns payBillSource
+    }
+}