Enable FindBugs in tests.

This would have caught the unused variable that was fixed by #1082.

Changes in this commit:

  - Enable FindBugs in tests in build.gradle.

  - Fix some existing minor FindBugs issues in tests.

  - Suppress some warnings in all test classes that are less important in test
    code, such as requiring nested classes to be static whenever possible.

  - Enable nullness-related FindBugs warnings in tests, since we don't run the
    Checker Framework on test code.

4 files changed, 10 insertions, 8 deletions

diff --git a/impl_core/src/test/java/io/opencensus/implcore/stats/StatsTestUtil.java b/impl_core/src/test/java/io/opencensus/implcore/stats/StatsTestUtil.java
index 848fdd7b..1d57dbe2 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/stats/StatsTestUtil.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/stats/StatsTestUtil.java
@@ -40,6 +40,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import javax.annotation.Nullable;
 
 /** Stats test utilities. */
@@ -76,8 +77,9 @@ final class StatsTestUtil {
       Map<? extends List<? extends TagValue>, ? extends AggregationData> expected,
       double tolerance) {
     assertThat(actual.keySet()).containsExactlyElementsIn(expected.keySet());
-    for (List<? extends TagValue> tagValues : actual.keySet()) {
-      assertAggregationDataEquals(expected.get(tagValues), actual.get(tagValues), tolerance);
+    for (Entry<? extends List<? extends TagValue>, ? extends AggregationData> entry :
+        actual.entrySet()) {
+      assertAggregationDataEquals(expected.get(entry.getKey()), entry.getValue(), tolerance);
     }
   }
 
diff --git a/impl_core/src/test/java/io/opencensus/implcore/stats/ViewManagerImplTest.java b/impl_core/src/test/java/io/opencensus/implcore/stats/ViewManagerImplTest.java
index cfbd6735..2ec0da1a 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/stats/ViewManagerImplTest.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/stats/ViewManagerImplTest.java
@@ -97,7 +97,7 @@ public class ViewManagerImplTest {
   private static final Cumulative CUMULATIVE = Cumulative.create();
 
   private static final double EPSILON = 1e-7;
-  private static final int MILLIS_PER_SECOND = 1000;
+  private static final long MILLIS_PER_SECOND = 1000;
   private static final Duration TEN_SECONDS = Duration.create(10, 0);
   private static final Interval INTERVAL = Interval.create(TEN_SECONDS);
 
diff --git a/impl_core/src/test/java/io/opencensus/implcore/tags/propagation/TagContextSerializationTest.java b/impl_core/src/test/java/io/opencensus/implcore/tags/propagation/TagContextSerializationTest.java
index 771b2899..ed68fe3d 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/tags/propagation/TagContextSerializationTest.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/tags/propagation/TagContextSerializationTest.java
@@ -133,7 +133,7 @@ public class TagContextSerializationTest {
         encodeString(tag.getKey().getName(), expected);
         encodeString(tag.getValue().asString(), expected);
       }
-      possibleOutputs.add(expected.toString());
+      possibleOutputs.add(new String(expected.toByteArray(), Charsets.UTF_8));
     }
 
     assertThat(possibleOutputs).contains(new String(actual, Charsets.UTF_8));
diff --git a/impl_core/src/test/java/io/opencensus/implcore/trace/SpanImplTest.java b/impl_core/src/test/java/io/opencensus/implcore/trace/SpanImplTest.java
index 4517d273..355ace51 100644
--- a/impl_core/src/test/java/io/opencensus/implcore/trace/SpanImplTest.java
+++ b/impl_core/src/test/java/io/opencensus/implcore/trace/SpanImplTest.java
@@ -459,7 +459,7 @@ public class SpanImplTest {
     assertThat(spanData.getAnnotations().getEvents().size()).isEqualTo(maxNumberOfAnnotations);
     for (int i = 0; i < maxNumberOfAnnotations; i++) {
       assertThat(spanData.getAnnotations().getEvents().get(i).getTimestamp())
-          .isEqualTo(timestamp.addNanos(100 * (maxNumberOfAnnotations + i)));
+          .isEqualTo(timestamp.addNanos(100L * (maxNumberOfAnnotations + i)));
       assertThat(spanData.getAnnotations().getEvents().get(i).getEvent()).isEqualTo(annotation);
     }
     span.end();
@@ -468,7 +468,7 @@ public class SpanImplTest {
     assertThat(spanData.getAnnotations().getEvents().size()).isEqualTo(maxNumberOfAnnotations);
     for (int i = 0; i < maxNumberOfAnnotations; i++) {
       assertThat(spanData.getAnnotations().getEvents().get(i).getTimestamp())
-          .isEqualTo(timestamp.addNanos(100 * (maxNumberOfAnnotations + i)));
+          .isEqualTo(timestamp.addNanos(100L * (maxNumberOfAnnotations + i)));
       assertThat(spanData.getAnnotations().getEvents().get(i).getEvent()).isEqualTo(annotation);
     }
   }
@@ -504,7 +504,7 @@ public class SpanImplTest {
     assertThat(spanData.getNetworkEvents().getEvents().size()).isEqualTo(maxNumberOfNetworkEvents);
     for (int i = 0; i < maxNumberOfNetworkEvents; i++) {
       assertThat(spanData.getNetworkEvents().getEvents().get(i).getTimestamp())
-          .isEqualTo(timestamp.addNanos(100 * (maxNumberOfNetworkEvents + i)));
+          .isEqualTo(timestamp.addNanos(100L * (maxNumberOfNetworkEvents + i)));
       assertThat(spanData.getNetworkEvents().getEvents().get(i).getEvent()).isEqualTo(networkEvent);
     }
     span.end();
@@ -514,7 +514,7 @@ public class SpanImplTest {
     assertThat(spanData.getNetworkEvents().getEvents().size()).isEqualTo(maxNumberOfNetworkEvents);
     for (int i = 0; i < maxNumberOfNetworkEvents; i++) {
       assertThat(spanData.getNetworkEvents().getEvents().get(i).getTimestamp())
-          .isEqualTo(timestamp.addNanos(100 * (maxNumberOfNetworkEvents + i)));
+          .isEqualTo(timestamp.addNanos(100L * (maxNumberOfNetworkEvents + i)));
       assertThat(spanData.getNetworkEvents().getEvents().get(i).getEvent()).isEqualTo(networkEvent);
     }
   }