make channel unit tests

app/src/androidTest/java/com/geeksville/mesh/ChannelTest.kt

@@ -0,0 +1,22 @@
+package com.geeksville.mesh
+
+
+import androidx.compose.frames.open
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.geeksville.mesh.model.Channel
+import org.junit.Assert
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class ChannelTest {
+    @Test
+    fun channelUrlGood() {
+        open() // Needed to make Compose think we are inside a Frame
+        val ch = Channel.emulated
+
+        Assert.assertTrue(ch.getChannelUrl().toString().startsWith(Channel.prefix))
+        Assert.assertEquals(Channel(ch.getChannelUrl()), ch)
+    }
+
+}