For testing: add rule to mock timezone.

Used by ExportImportTest.csv_export_only()

src/androidTest/java/de/dennisguse/opentracks/TimezoneRule.java

@@ -0,0 +1,36 @@
+package de.dennisguse.opentracks;
+
+import androidx.annotation.NonNull;
+
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import java.util.TimeZone;
+
+public class TimezoneRule implements TestRule {
+
+    private final TimeZone mTimeZone;
+    private TimeZone mDeviceTimeZone;
+
+
+    public TimezoneRule(@NonNull TimeZone timeZone) {
+        mTimeZone = timeZone;
+    }
+
+    @Override
+    public Statement apply(Statement base, Description description) {
+        return new Statement() {
+            @Override
+            public void evaluate() throws Throwable {
+                try {
+                    mDeviceTimeZone = TimeZone.getDefault();
+                    TimeZone.setDefault(mTimeZone);
+                    base.evaluate();
+                } finally {
+                    TimeZone.setDefault(mDeviceTimeZone);
+                }
+            }
+        };
+    }
+}

src/androidTest/java/de/dennisguse/opentracks/io/file/importer/ExportImportTest.java

@@ -38,11 +38,13 @@ import java.time.Duration;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.TimeZone;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.stream.Collectors;
 
 import de.dennisguse.opentracks.R;
+import de.dennisguse.opentracks.TimezoneRule;
 import de.dennisguse.opentracks.content.data.TestDataUtil;
 import de.dennisguse.opentracks.data.ContentProviderUtils;
 import de.dennisguse.opentracks.data.models.Cadence;
@@ -78,6 +80,10 @@ public class ExportImportTest {
     @Rule
     public GrantPermissionRule mRuntimePermissionRule = GrantPermissionRule.grant(android.Manifest.permission.ACCESS_FINE_LOCATION);
 
+    //For csv_export_only() as we the timezone is hardcoded in the expectation.
+    @Rule
+    public TimezoneRule timezoneRule = new TimezoneRule(TimeZone.getTimeZone("Europe/Berlin"));
+
     @BeforeClass
     public static void preSetUp() {
         // Prepare looper for Android's message queue