diff --git a/tools/chatgui-android/app/src/test/java/com/utun/chat/data/H264AnnexBTest.kt b/tools/chatgui-android/app/src/test/java/com/utun/chat/data/H264AnnexBTest.kt
new file mode 100644
index 00000000..7bc8cc50
--- /dev/null
+++ b/tools/chatgui-android/app/src/test/java/com/utun/chat/data/H264AnnexBTest.kt
@@ -0,0 +1,33 @@
+package com.utun.chat.data
+
+import org.junit.Assert.*
+import org.junit.Test
+
+class H264AnnexBTest {
+    private val sps = byteArrayOf(0, 0, 0, 1, 0x67, 0x42, 0, 0x1f)
+    private val pps = byteArrayOf(0, 0, 1, 0x68, 0x11)
+    private val idr = byteArrayOf(0, 0, 0, 1, 0x65, 0x22, 0x33)
+
+    @Test fun joinsConfigurationWithEveryKeyFrame() {
+        val output = H264AnnexB.keyFrame(idr, sps + pps)
+        assertEquals(listOf(7, 8, 5), H264AnnexB.nals(output).map { it.first })
+        assertArrayEquals(output, H264AnnexB.keyFrame(output, sps + pps))
+        assertArrayEquals(sps, H264AnnexB.nals(output).first().second)
+    }
+
+    @Test fun convertsLengthPrefixedAccessUnits() {
+        val avcc = byteArrayOf(0, 0, 0, 3, 0x65, 0x22, 0x33, 0, 0, 0, 2, 0x61, 0x11)
+        assertEquals(listOf(5, 1), H264AnnexB.nals(H264AnnexB.normalize(avcc)).map { it.first })
+        assertArrayEquals(idr, H264AnnexB.normalize(avcc.copyOfRange(0, 7)))
+    }
+
+    @Test fun rejectsTruncatedAndMissingConfiguration() {
+        for (data in listOf(byteArrayOf(), byteArrayOf(0, 0, 1), byteArrayOf(0, 0, 0, 5, 0x65),
+            byteArrayOf(0x7f, -1, -1, -1, 0x65), byteArrayOf(0, 0, 0, 1, -1))) {
+            assertThrows(IllegalArgumentException::class.java) { H264AnnexB.normalize(data) }
+        }
+        assertThrows(IllegalArgumentException::class.java) { H264AnnexB.keyFrame(idr, sps) }
+        assertThrows(IllegalArgumentException::class.java) { H264AnnexB.keyFrame(byteArrayOf(0, 0, 1, 0x61, 0x11), sps + pps) }
+        assertThrows(IllegalArgumentException::class.java) { H264AnnexB.normalize(ByteArray(H264AnnexB.MAX_FRAME + 1)) }
+    }
+}