test: added unit tests for the PowerUtils util class.

Signed-off-by: ardevd <edvard.holst@gmail.com>

src/test/java/com/owncloud/android/utils/PowerUtilsTest.java

@@ -0,0 +1,58 @@
+package com.owncloud.android.utils;
+
+import android.content.Context;
+import android.os.Build;
+import android.os.PowerManager;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.when;
+
+public class PowerUtilsTest {
+
+    @Mock
+    private Context mContext;
+
+    @Mock
+    private PowerManager mPowerManager;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    private static void setFinalStatic(Field field, Object newValue) throws Exception {
+        field.setAccessible(true);
+
+        Field modifiersField = Field.class.getDeclaredField("modifiers");
+        modifiersField.setAccessible(true);
+        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
+
+        field.set(null, newValue);
+    }
+
+    @Test
+    public void isPowerSaveMode_assertCorrectlyReportsTrue() throws Exception {
+        setFinalStatic(Build.VERSION.class.getField("SDK_INT"), Build.VERSION_CODES.O);
+        when(mContext.getSystemService(Context.POWER_SERVICE)).thenReturn(mPowerManager);
+        when(mPowerManager.isPowerSaveMode()).thenReturn(true);
+        assertTrue("Incorrectly reported power saving mode on",
+                   PowerUtils.isPowerSaveMode(mContext));
+    }
+
+    @Test
+    public void isPowerSaveMode_assertCorrectlyReportsFalse() throws Exception {
+        setFinalStatic(Build.VERSION.class.getField("SDK_INT"), Build.VERSION_CODES.O);
+        when(mContext.getSystemService(Context.POWER_SERVICE)).thenReturn(mPowerManager);
+        when(mPowerManager.isPowerSaveMode()).thenReturn(false);
+        assertFalse("Incorrectly reported power saving mode off",
+                    PowerUtils.isPowerSaveMode(mContext));
+    }
+}