diff --git a/app/build.gradle b/app/build.gradle
index d4b18b1df0..3289276b59 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -214,6 +214,7 @@ dependencies {
     testCompile "org.powermock:powermock-module-junit4-rule:${powermockVersion}"
     testCompile "org.powermock:powermock-module-junit4:${powermockVersion}"
     testCompile "joda-time:joda-time:2.9.4.2"
+    testCompile "com.google.truth:truth:0.39"
 
     androidTestCompile "org.mockito:mockito-core:2.7.22"
     androidTestCompile "com.google.dexmaker:dexmaker:${dexmakerVersion}"
diff --git a/app/src/test/java/info/nightscout/androidaps/plugins/PumpInsight/HelpersTest.java b/app/src/test/java/info/nightscout/androidaps/plugins/PumpInsight/HelpersTest.java
new file mode 100644
index 0000000000..885edfac61
--- /dev/null
+++ b/app/src/test/java/info/nightscout/androidaps/plugins/PumpInsight/HelpersTest.java
@@ -0,0 +1,31 @@
+package info.nightscout.androidaps.plugins.PumpInsight;
+
+
+import com.google.common.truth.Truth;
+
+import org.junit.Test;
+
+import static info.nightscout.androidaps.plugins.PumpInsight.utils.Helpers.roundDouble;
+
+/**
+ * Created by jamorham on 26.01.2018.
+ */
+
+public class HelpersTest {
+
+    @Test
+    public void checkRounding() throws Exception {
+
+        // TODO more test cases including known precision breakdowns
+
+        Truth.assertThat(roundDouble(Double.parseDouble("0.999999"),0))
+                .isEqualTo(1d);
+
+        Truth.assertThat(roundDouble(Double.parseDouble("0.123456"),0))
+                .isEqualTo(0d);
+
+    }
+
+
+
+}
\ No newline at end of file