Improve test coverage

Author: tylerbenson

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/export/PeriodicMetricReader.java

@@ -82,19 +82,19 @@ public MemoryMode getMemoryMode() {
   @Override
   public CompletableResultCode forceFlush() {
     CompletableResultCode result = new CompletableResultCode();
-    CompletableResultCode flushResult = scheduled.doRun();
-    flushResult.whenComplete(
-        () ->
-            exporter
-                .flush()
-                .whenComplete(
-                    () -> {
-                      if (!flushResult.isSuccess()) {
-                        result.fail();
-                      } else {
-                        result.succeed();
-                      }
-                    }));
+    CompletableResultCode doRunResult = scheduled.doRun();
+    doRunResult.whenComplete(
+        () -> {
+          CompletableResultCode flushResult = exporter.flush();
+          flushResult.whenComplete(
+              () -> {
+                if (doRunResult.isSuccess() && flushResult.isSuccess()) {
+                  result.succeed();
+                } else {
+                  result.fail();
+                }
+              });
+        });
     return result;
   }
 

sdk/metrics/src/test/java/io/opentelemetry/sdk/metrics/export/PeriodicMetricReaderTest.java

@@ -157,23 +157,30 @@ void flush() throws Exception {
   @Test
   void forceflush_callsFlush() {
     MetricExporter metricExporter = mock(MetricExporter.class);
-    when(metricExporter.export(any())).thenReturn(CompletableResultCode.ofSuccess());
-    when(metricExporter.flush()).thenReturn(CompletableResultCode.ofSuccess());
+    when(metricExporter.export(any()))
+        .thenReturn(CompletableResultCode.ofSuccess())
+        .thenReturn(CompletableResultCode.ofSuccess())
+        .thenThrow(new RuntimeException("Export Failed!"));
+    when(metricExporter.flush())
+        .thenReturn(CompletableResultCode.ofSuccess())
+        .thenReturn(CompletableResultCode.ofFailure())
+        .thenReturn(CompletableResultCode.ofSuccess());
     when(metricExporter.shutdown()).thenReturn(CompletableResultCode.ofSuccess());
 
     PeriodicMetricReader reader =
         PeriodicMetricReader.builder(metricExporter)
             .setInterval(Duration.ofNanos(Long.MAX_VALUE))
             .build();
 
-    reader.register(collectionRegistration);
-    assertThat(reader.forceFlush().join(10, TimeUnit.SECONDS).isSuccess()).isTrue();
-
     try {
-      verify(metricExporter).flush();
+      reader.register(collectionRegistration);
+      assertThat(reader.forceFlush().join(10, TimeUnit.SECONDS).isSuccess()).isTrue();
+      assertThat(reader.forceFlush().join(10, TimeUnit.SECONDS).isSuccess()).isFalse();
+      assertThat(reader.forceFlush().join(10, TimeUnit.SECONDS).isSuccess()).isFalse();
     } finally {
       reader.shutdown();
     }
+    verify(metricExporter, times(3)).flush();
   }
 
   @Test