test: add unit tests for SystemViewModel update confirm state toggles (#509)

Added SystemViewModelTest to provide basic testing coverage for the
openUpdateConfirm and closeUpdateConfirm methods. These methods
handle state changes within the UI without side-effects or
dependencies, so straightforward property assertions were sufficient.

This improves overall code reliability by ensuring simple UI boolean
states function predictably.

app/src/test/java/com/m57/hermescontrol/ui/system/SystemViewModelTest.kt

@@ -0,0 +1,51 @@
+package com.m57.hermescontrol.ui.system
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class SystemViewModelTest {
+    private val testDispatcher = StandardTestDispatcher()
+
+    @Before
+    fun setup() {
+        Dispatchers.setMain(testDispatcher)
+    }
+
+    @After
+    fun teardown() {
+        Dispatchers.resetMain()
+    }
+
+    @Test
+    fun `openUpdateConfirm sets updateConfirmOpen to true`() {
+        val viewModel = SystemViewModel()
+
+        assertFalse(viewModel.uiState.value.updateConfirmOpen)
+
+        viewModel.openUpdateConfirm()
+
+        assertTrue(viewModel.uiState.value.updateConfirmOpen)
+    }
+
+    @Test
+    fun `closeUpdateConfirm sets updateConfirmOpen to false`() {
+        val viewModel = SystemViewModel()
+
+        // First open it
+        viewModel.openUpdateConfirm()
+        assertTrue(viewModel.uiState.value.updateConfirmOpen)
+
+        // Then close it
+        viewModel.closeUpdateConfirm()
+        assertFalse(viewModel.uiState.value.updateConfirmOpen)
+    }
+}