diff --git a/app/src/main/java/info/nightscout/androidaps/utils/ResourceHelper.kt b/app/src/main/java/info/nightscout/androidaps/utils/ResourceHelper.kt
index 655c319170..a718a0803e 100644
--- a/app/src/main/java/info/nightscout/androidaps/utils/ResourceHelper.kt
+++ b/app/src/main/java/info/nightscout/androidaps/utils/ResourceHelper.kt
@@ -9,7 +9,7 @@ import javax.inject.Inject
 /**
  * Created by adrian on 2019-12-23.
  */
-class ResourceHelper @Inject constructor() {
+open class ResourceHelper @Inject constructor() {
 
     fun gs(@StringRes id: Int): String = MainApp.sResources.getString(id)
 
diff --git a/app/src/test/java/info/nightscout/androidaps/plugins/insulin/InsulinOrefFreePeakPluginTest.kt b/app/src/test/java/info/nightscout/androidaps/plugins/insulin/InsulinOrefFreePeakPluginTest.kt
new file mode 100644
index 0000000000..806c8e0379
--- /dev/null
+++ b/app/src/test/java/info/nightscout/androidaps/plugins/insulin/InsulinOrefFreePeakPluginTest.kt
@@ -0,0 +1,60 @@
+package info.nightscout.androidaps.plugins.insulin
+
+import info.nightscout.androidaps.R
+import info.nightscout.androidaps.utils.ResourceHelper
+import info.nightscout.androidaps.utils.sharedPreferences.SP
+import junit.framework.Assert.assertEquals
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.mockito.ArgumentMatchers.anyInt
+import org.mockito.ArgumentMatchers.eq
+import org.mockito.Mock
+import org.mockito.Mockito
+import org.mockito.Mockito.`when`
+import org.mockito.junit.MockitoJUnit
+import org.mockito.junit.MockitoRule
+
+/**
+ * Created by adrian on 2019-12-25.
+ */
+
+class InsulinOrefFreePeakPluginTest {
+
+
+    // TODO: move to a base class
+    // Add a JUnit rule that will setup the @Mock annotated vars and log.
+    // Another possibility would be to add `MockitoAnnotations.initMocks(this) to the setup method.
+    @get:Rule
+    val mockitoRule: MockitoRule = MockitoJUnit.rule()
+
+    lateinit var sut: InsulinOrefFreePeakPlugin
+
+    @Mock
+    lateinit var sp: SP
+
+    @Mock
+    lateinit var resourceHelper: ResourceHelper
+
+    @Before
+    fun setup() {
+        sut = InsulinOrefFreePeakPlugin(sp, resourceHelper)
+    }
+
+    @Test
+    fun `simple peak test`() {
+        `when`(sp.getInt(eq(R.string.key_insulin_oref_peak), anyInt())).thenReturn(90)
+        assertEquals(90, sut.peak)
+    }
+
+    // Workaround for Kotlin nullability. TODO: move to a base class
+    // https://medium.com/@elye.project/befriending-kotlin-and-mockito-1c2e7b0ef791
+    // https://stackoverflow.com/questions/30305217/is-it-possible-to-use-mockito-in-kotlin
+    private fun <T> anyObject(): T {
+        Mockito.any<T>()
+        return uninitialized()
+    }
+
+    private fun <T> uninitialized(): T = null as T
+
+}
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