feat: Enhance test coverage (#4847)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

core/network/src/commonTest/kotlin/org/meshtastic/core/network/radio/StreamInterfaceTest.kt

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.core.network.radio
+
+import dev.mokkery.MockMode
+import dev.mokkery.answering.returns
+import dev.mokkery.every
+import dev.mokkery.mock
+import dev.mokkery.verify
+import io.kotest.property.Arb
+import io.kotest.property.arbitrary.byte
+import io.kotest.property.arbitrary.byteArray
+import io.kotest.property.arbitrary.int
+import io.kotest.property.checkAll
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
+import org.meshtastic.core.network.transport.StreamFrameCodec
+import org.meshtastic.core.repository.RadioInterfaceService
+import kotlin.test.BeforeTest
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+class StreamInterfaceTest {
+
+    private val radioService: RadioInterfaceService = mock(MockMode.autofill)
+    private lateinit var fakeStream: FakeStreamInterface
+
+    class FakeStreamInterface(service: RadioInterfaceService) : StreamInterface(service) {
+        val sentBytes = mutableListOf<ByteArray>()
+
+        override fun sendBytes(p: ByteArray) {
+            sentBytes.add(p)
+        }
+
+        override fun flushBytes() {
+            /* no-op */
+        }
+
+        override fun keepAlive() {
+            /* no-op */
+        }
+
+        fun feed(b: Byte) = readChar(b)
+
+        public override fun connect() = super.connect()
+    }
+
+    @BeforeTest
+    fun setUp() {
+        every { radioService.serviceScope } returns TestScope()
+    }
+
+    @Test
+    fun `handleSendToRadio property test`() = runTest {
+        fakeStream = FakeStreamInterface(radioService)
+
+        checkAll(Arb.byteArray(Arb.int(0, 512), Arb.byte())) { payload -> fakeStream.handleSendToRadio(payload) }
+    }
+
+    @Test
+    fun `readChar property test`() = runTest {
+        fakeStream = FakeStreamInterface(radioService)
+
+        checkAll(Arb.byteArray(Arb.int(0, 100), Arb.byte())) { data ->
+            data.forEach { fakeStream.feed(it) }
+            // Ensure no crash
+        }
+    }
+
+    @Test
+    fun `connect sends wake bytes`() {
+        fakeStream = FakeStreamInterface(radioService)
+        fakeStream.connect()
+
+        assertTrue(fakeStream.sentBytes.isNotEmpty())
+        assertTrue(fakeStream.sentBytes[0].contentEquals(StreamFrameCodec.WAKE_BYTES))
+        verify { radioService.onConnect() }
+    }
+}

core/network/src/commonTest/kotlin/org/meshtastic/core/network/transport/StreamFrameCodecTest.kt

@@ -16,6 +16,14 @@
  */
 package org.meshtastic.core.network.transport
 
+import io.kotest.matchers.nulls.shouldNotBeNull
+import io.kotest.matchers.shouldBe
+import io.kotest.property.Arb
+import io.kotest.property.arbitrary.byte
+import io.kotest.property.arbitrary.byteArray
+import io.kotest.property.arbitrary.int
+import io.kotest.property.checkAll
+import kotlinx.coroutines.test.runTest
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
@@ -56,6 +64,31 @@ class StreamFrameCodecTest {
         assertEquals(listOf(0x55.toByte()), receivedPackets[0].toList())
     }
 
+    @Test
+    fun `frameAndSend and processInputByte are inverse`() = runTest {
+        checkAll(Arb.byteArray(Arb.int(0, 512), Arb.byte())) { payload ->
+            var received: ByteArray? = null
+            val codec = StreamFrameCodec(onPacketReceived = { received = it })
+
+            val bytes = mutableListOf<ByteArray>()
+            codec.frameAndSend(payload, sendBytes = { bytes.add(it) })
+
+            bytes.forEach { arr -> arr.forEach { codec.processInputByte(it) } }
+
+            received.shouldNotBeNull()
+            received.shouldBe(payload)
+        }
+    }
+
+    @Test
+    fun `processInputByte is robust against random noise`() = runTest {
+        checkAll(Arb.byteArray(Arb.int(0, 1000), Arb.byte())) { noise ->
+            val codec = StreamFrameCodec(onPacketReceived = { /* ignore */ })
+            noise.forEach { codec.processInputByte(it) }
+            // Should not crash
+        }
+    }
+
     @Test
     fun `processInputByte handles multiple packets sequentially`() {
         val packet1 = byteArrayOf(0x94.toByte(), 0xc3.toByte(), 0x00, 0x01, 0x11)