Adds test missing from last PR

spring-cloud-sleuth-zipkin-stream/src/test/java/org/springframework/cloud/sleuth/zipkin/stream/SamplingZipkinSpanIteratorTests.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.cloud.sleuth.zipkin.stream;
+
+import io.zipkin.Sampler;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.Test;
+import org.springframework.cloud.sleuth.MilliSpan;
+import org.springframework.cloud.sleuth.Span;
+import org.springframework.cloud.sleuth.stream.Host;
+import org.springframework.cloud.sleuth.stream.Spans;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SamplingZipkinSpanIteratorTests {
+
+  Host host = new Host("myservice", "1.2.3.4", 8080);
+
+  @Test
+  public void skipsInputSpans() {
+    Spans spans = new Spans(host, Arrays.asList(span("message/sleuth")));
+
+    Iterator<io.zipkin.Span> result = new SamplingZipkinSpanIterator(Sampler.create(1.0f), spans);
+
+    assertThat(result).isEmpty();
+  }
+
+  @Test
+  public void retainsValidSpans() {
+    Spans spans = new Spans(host, Arrays.asList(span("foo"), span("bar"), span("baz")));
+
+    Iterator<io.zipkin.Span> result = new SamplingZipkinSpanIterator(Sampler.create(1.0f), spans);
+
+    assertThat(result).extracting(s -> s.name).containsExactly("foo", "bar", "baz");
+  }
+
+  @Test
+  public void retainsOnlySampledSpans() {
+    Spans spans = new Spans(host, Arrays.asList(span("foo"), span("bar"), span("baz")));
+
+    Sampler everyOtherSampler = new Sampler() {
+      AtomicInteger counter = new AtomicInteger();
+
+      public boolean isSampled(long l) {
+        return counter.getAndIncrement() % 2 == 0;
+      }
+    };
+
+    Iterator<io.zipkin.Span> result = new SamplingZipkinSpanIterator(everyOtherSampler, spans);
+
+    assertThat(result).extracting(s -> s.name).containsExactly("foo", "baz");
+  }
+
+  Span span(String name) {
+    String id = UUID.randomUUID().toString();
+    return new MilliSpan(1, 3, name, id, Collections.<String>emptyList(), id, true, true, "proc");
+  }
+}