test: Add comprehensive unit tests

- IdleTimerTest.kt: 6 tests for timeout calculations
- ConfigValidationTest.kt: 16 tests for config validation
  - Homepage URL validation
  - Admin PIN validation (4-8 digits)
  - Whitelist parsing and normalization
- Updated IMPROVEMENTS.md with test coverage

Total unit tests: 29

app/src/test/kotlin/farm/hobbs/kioskbrowser/ConfigValidationTest.kt

@@ -0,0 +1,135 @@
+package farm.hobbs.kioskbrowser
+
+import org.junit.Assert.*
+import org.junit.Test
+
+/**
+ * Unit tests for configuration validation
+ */
+class ConfigValidationTest {
+
+    /**
+     * Validate homepage URL format
+     */
+    private fun isValidHomepage(url: String): Boolean {
+        return url.startsWith("http://") || url.startsWith("https://")
+    }
+
+    /**
+     * Validate admin PIN (numeric, 4-8 digits)
+     */
+    private fun isValidPin(pin: String): Boolean {
+        return pin.matches(Regex("^\\d{4,8}$"))
+    }
+
+    /**
+     * Parse whitelist from comma-separated string
+     */
+    private fun parseWhitelist(input: String): List<String> {
+        return input.split(",")
+            .map { it.trim().lowercase() }
+            .filter { it.isNotEmpty() }
+    }
+
+    // Homepage validation tests
+    @Test
+    fun `valid https homepage`() {
+        assertTrue(isValidHomepage("https://hobbs.farm"))
+        assertTrue(isValidHomepage("https://example.com/path"))
+    }
+
+    @Test
+    fun `valid http homepage`() {
+        assertTrue(isValidHomepage("http://localhost:8080"))
+        assertTrue(isValidHomepage("http://192.168.1.1"))
+    }
+
+    @Test
+    fun `invalid homepage without protocol`() {
+        assertFalse(isValidHomepage("hobbs.farm"))
+        assertFalse(isValidHomepage("www.example.com"))
+    }
+
+    @Test
+    fun `invalid homepage with wrong protocol`() {
+        assertFalse(isValidHomepage("ftp://files.example.com"))
+        assertFalse(isValidHomepage("file:///path/to/file"))
+    }
+
+    // PIN validation tests
+    @Test
+    fun `valid 4 digit PIN`() {
+        assertTrue(isValidPin("1234"))
+        assertTrue(isValidPin("0000"))
+    }
+
+    @Test
+    fun `valid 6 digit PIN`() {
+        assertTrue(isValidPin("123456"))
+    }
+
+    @Test
+    fun `valid 8 digit PIN`() {
+        assertTrue(isValidPin("12345678"))
+    }
+
+    @Test
+    fun `invalid PIN too short`() {
+        assertFalse(isValidPin("123"))
+        assertFalse(isValidPin("1"))
+    }
+
+    @Test
+    fun `invalid PIN too long`() {
+        assertFalse(isValidPin("123456789"))
+    }
+
+    @Test
+    fun `invalid PIN with letters`() {
+        assertFalse(isValidPin("12ab"))
+        assertFalse(isValidPin("abcd"))
+    }
+
+    @Test
+    fun `invalid PIN with special characters`() {
+        assertFalse(isValidPin("12-34"))
+        assertFalse(isValidPin("1234!"))
+    }
+
+    // Whitelist parsing tests
+    @Test
+    fun `parse single domain`() {
+        val result = parseWhitelist("hobbs.farm")
+        assertEquals(listOf("hobbs.farm"), result)
+    }
+
+    @Test
+    fun `parse multiple domains`() {
+        val result = parseWhitelist("hobbs.farm, example.com, test.org")
+        assertEquals(listOf("hobbs.farm", "example.com", "test.org"), result)
+    }
+
+    @Test
+    fun `parse whitelist normalizes case`() {
+        val result = parseWhitelist("HOBBS.FARM, Example.Com")
+        assertEquals(listOf("hobbs.farm", "example.com"), result)
+    }
+
+    @Test
+    fun `parse whitelist handles extra whitespace`() {
+        val result = parseWhitelist("  hobbs.farm  ,  example.com  ")
+        assertEquals(listOf("hobbs.farm", "example.com"), result)
+    }
+
+    @Test
+    fun `parse whitelist filters empty entries`() {
+        val result = parseWhitelist("hobbs.farm,,example.com,")
+        assertEquals(listOf("hobbs.farm", "example.com"), result)
+    }
+
+    @Test
+    fun `parse empty whitelist`() {
+        val result = parseWhitelist("")
+        assertTrue(result.isEmpty())
+    }
+}

app/src/test/kotlin/farm/hobbs/kioskbrowser/IdleTimerTest.kt

@@ -0,0 +1,48 @@
+package farm.hobbs.kioskbrowser
+
+import org.junit.Assert.*
+import org.junit.Test
+
+/**
+ * Unit tests for idle timer calculations and behavior
+ */
+class IdleTimerTest {
+
+    /**
+     * Convert minutes to milliseconds for idle timeout
+     */
+    private fun calculateTimeoutMs(minutes: Int): Long {
+        return if (minutes <= 0) 0L else minutes * 60 * 1000L
+    }
+
+    @Test
+    fun `zero timeout disables timer`() {
+        assertEquals(0L, calculateTimeoutMs(0))
+    }
+
+    @Test
+    fun `negative timeout disables timer`() {
+        assertEquals(0L, calculateTimeoutMs(-5))
+        assertEquals(0L, calculateTimeoutMs(-1))
+    }
+
+    @Test
+    fun `1 minute timeout converts correctly`() {
+        assertEquals(60_000L, calculateTimeoutMs(1))
+    }
+
+    @Test
+    fun `5 minute default timeout converts correctly`() {
+        assertEquals(300_000L, calculateTimeoutMs(5))
+    }
+
+    @Test
+    fun `30 minute timeout converts correctly`() {
+        assertEquals(1_800_000L, calculateTimeoutMs(30))
+    }
+
+    @Test
+    fun `60 minute timeout converts correctly`() {
+        assertEquals(3_600_000L, calculateTimeoutMs(60))
+    }
+}