add distance unit test and fix bug reported via crashyltics

app/src/main/java/com/geeksville/mesh/NodeInfo.kt

@@ -125,7 +125,7 @@ data class NodeInfo(
     fun distanceStr(o: NodeInfo?) = distance(o)?.let { dist ->
         when {
             dist == 0 -> null // same point
-            dist < 1000 -> "%.0f m".format(dist)
+            dist < 1000 -> "%.0f m".format(dist.toDouble())
             else -> "%.1f km".format(dist / 1000.0)
         }
     }

app/src/test/java/com/geeksville/mesh/NodeInfoTest.kt

@@ -0,0 +1,22 @@
+package com.geeksville.mesh
+
+import org.junit.Assert
+import org.junit.Test
+
+class NodeInfoTest {
+    val ni1 = NodeInfo(4, MeshUser("+one", "User One", "U1"), Position(37.1, 121.1, 35))
+    val ni2 = NodeInfo(5, MeshUser("+two", "User Two", "U2"), Position(37.11, 121.1, 40))
+    val ni3 = NodeInfo(6, MeshUser("+three", "User Three", "U3"), Position(37.101, 121.1, 40))
+
+    @Test
+    fun distanceGood() {
+        Assert.assertEquals(ni1.distance(ni2), 1111)
+        Assert.assertEquals(ni1.distance(ni3), 111)
+    }
+
+    @Test
+    fun distanceStrGood() {
+        Assert.assertEquals(ni1.distanceStr(ni2), "1.1 km")
+        Assert.assertEquals(ni1.distanceStr(ni3), "111 m")
+    }
+}