Update group membership for a group call when it changes.

app/src/test/java/org/thoughtcrime/securesms/util/livedata/LiveDataUtilTest_skip.java

@@ -0,0 +1,120 @@
+package org.thoughtcrime.securesms.util.livedata;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TestRule;
+
+import static org.junit.Assert.assertEquals;
+import static org.thoughtcrime.securesms.util.livedata.LiveDataTestUtil.assertNoValue;
+import static org.thoughtcrime.securesms.util.livedata.LiveDataTestUtil.observeAndGetOneValue;
+
+public final class LiveDataUtilTest_skip {
+
+  @Rule
+  public TestRule rule = new LiveDataRule();
+
+  @Test
+  public void skip_no_value() {
+    MutableLiveData<String> liveData = new MutableLiveData<>();
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 0);
+
+    assertNoValue(skipped);
+  }
+
+  @Test
+  public void skip_same_value_with_zero_skip() {
+    MutableLiveData<String> liveData = new MutableLiveData<>();
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 0);
+    liveData.setValue("A");
+
+    assertEquals("A", observeAndGetOneValue(skipped));
+  }
+
+  @Test
+  public void skip_second_value_with_skip_one() {
+    MutableLiveData<String> liveData     = new MutableLiveData<>();
+    TestObserver<String>    testObserver = new TestObserver<>();
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 1);
+
+    skipped.observeForever(testObserver);
+    liveData.setValue("A");
+    liveData.setValue("B");
+    skipped.removeObserver(testObserver);
+
+    Assertions.assertThat(testObserver.getValues())
+              .containsExactly("B");
+  }
+
+  @Test
+  public void skip_no_value_with_skip() {
+    MutableLiveData<String> liveData = new MutableLiveData<>();
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 1);
+    liveData.setValue("A");
+
+    assertNoValue(skipped);
+  }
+
+  @Test
+  public void skip_third_and_fourth_value_with_skip_two() {
+    MutableLiveData<String> liveData     = new MutableLiveData<>();
+    TestObserver<String>    testObserver = new TestObserver<>();
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 2);
+
+    skipped.observeForever(testObserver);
+    liveData.setValue("A");
+    liveData.setValue("B");
+    liveData.setValue("C");
+    liveData.setValue("D");
+    skipped.removeObserver(testObserver);
+
+    Assertions.assertThat(testObserver.getValues())
+              .containsExactly("C", "D");
+  }
+
+  @Test
+  public void skip_set_one_before_then_skip() {
+    MutableLiveData<String> liveData     = new MutableLiveData<>();
+    TestObserver<String>    testObserver = new TestObserver<>();
+
+    liveData.setValue("A");
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 2);
+
+    skipped.observeForever(testObserver);
+    liveData.setValue("B");
+    liveData.setValue("C");
+    liveData.setValue("D");
+    skipped.removeObserver(testObserver);
+
+    Assertions.assertThat(testObserver.getValues())
+              .containsExactly("C", "D");
+  }
+
+  @Test
+  public void skip_set_two_before_then_skip() {
+    MutableLiveData<String> liveData     = new MutableLiveData<>();
+    TestObserver<String>    testObserver = new TestObserver<>();
+
+    liveData.setValue("A");
+    liveData.setValue("B");
+
+    LiveData<String> skipped = LiveDataUtil.skip(liveData, 2);
+
+    skipped.observeForever(testObserver);
+    liveData.setValue("C");
+    liveData.setValue("D");
+    skipped.removeObserver(testObserver);
+
+    Assertions.assertThat(testObserver.getValues())
+              .containsExactly("D");
+  }
+}

app/src/test/java/org/thoughtcrime/securesms/util/livedata/TestObserver.java

@@ -0,0 +1,22 @@
+package org.thoughtcrime.securesms.util.livedata;
+
+import androidx.lifecycle.Observer;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.util.Collection;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+public class TestObserver<T> implements Observer<T> {
+
+  private final Collection<T> values = new ConcurrentLinkedQueue<>();
+
+  @Override
+  public void onChanged(T t) {
+    values.add(t);
+  }
+
+  public @NonNull Collection<T> getValues() {
+    return values;
+  }
+}