junit: Add @FuzzTest#maxExecutions

Similar to `maxDuration`, this provides a more reliable way to limit the
logical amount of fuzzing performed per run. It will be used in a test
in a follow-up commit.

Author: fmeum

src/main/java/com/code_intelligence/jazzer/junit/AgentConfiguringArgumentsProvider.java

@@ -37,7 +37,8 @@ public Stream<? extends Arguments> provideArguments(ExtensionContext extensionCo
     // FIXME(fmeum): Calling this here feels like a hack. There should be a lifecycle hook that runs
     //  before the argument discovery for a ParameterizedTest is kicked off, but I haven't found
     //  one.
-    FuzzTestExecutor.configureAndInstallAgent(extensionContext, fuzzTest.maxDuration());
+    FuzzTestExecutor.configureAndInstallAgent(
+        extensionContext, fuzzTest.maxDuration(), fuzzTest.maxExecutions());
     return Stream.empty();
   }
 }

src/main/java/com/code_intelligence/jazzer/junit/FuzzTest.java

@@ -103,9 +103,22 @@
    * A duration string such as "1h 2m 30s" indicating for how long the fuzz test should be executed
    * during fuzzing.
    *
+   * <p>To remove the default limit of 5 minutes, set this element to {@code ""}.
+   *
    * <p>This option has no effect during regression testing.
    */
   String maxDuration() default "5m";
+
+  /**
+   * If set to a positive number, the fuzz test function will be executed at most this many times
+   * during fuzzing. Otherwise (default), there is no bound on the number of executions.
+   *
+   * <p>Prefer this element over {@link #maxDuration()} if you want to ensure comparable levels of
+   * fuzzing across machine's with different performance characteristics.
+   *
+   * <p>This option has no effect during regression testing.
+   */
+  long maxExecutions() default 0;
 }
 
 // Internal use only.

src/main/java/com/code_intelligence/jazzer/junit/FuzzTestExecutor.java

@@ -70,7 +70,7 @@ private FuzzTestExecutor(
     this.isRunFromCommandLine = isRunFromCommandLine;
   }
 
-  public static FuzzTestExecutor prepare(ExtensionContext context, String maxDuration)
+  public static FuzzTestExecutor prepare(ExtensionContext context, String maxDuration, long maxRuns)
       throws IOException {
     if (!hasBeenPrepared.compareAndSet(false, true)) {
       throw new IllegalStateException(
@@ -113,6 +113,9 @@ public static FuzzTestExecutor prepare(ExtensionContext context, String maxDurat
     }
 
     libFuzzerArgs.add("-max_total_time=" + durationStringToSeconds(maxDuration));
+    if (maxRuns > 0) {
+      libFuzzerArgs.add("-runs=" + maxRuns);
+    }
     // Disable libFuzzer's out of memory detection: It is only useful for native library fuzzing,
     // which we don't support without our native driver, and leads to false positives where it picks
     // up IntelliJ's memory usage.
@@ -256,13 +259,13 @@ private static List<String> getLibFuzzerArgs(ExtensionContext extensionContext)
     return args;
   }
 
-  static void configureAndInstallAgent(ExtensionContext extensionContext, String maxDuration)
-      throws IOException {
+  static void configureAndInstallAgent(ExtensionContext extensionContext, String maxDuration,
+      long maxExecutions) throws IOException {
     if (!agentInstalled.compareAndSet(false, true)) {
       return;
     }
     if (Utils.isFuzzing(extensionContext)) {
-      FuzzTestExecutor executor = prepare(extensionContext, maxDuration);
+      FuzzTestExecutor executor = prepare(extensionContext, maxDuration, maxExecutions);
       extensionContext.getRoot().getStore(Namespace.GLOBAL).put(FuzzTestExecutor.class, executor);
       AgentConfigurator.forFuzzing(extensionContext);
     } else {

src/main/java/com/code_intelligence/jazzer/junit/FuzzTestExtensions.java

@@ -44,7 +44,8 @@ public void interceptTestTemplateMethod(Invocation<Void> invocation,
       throws Throwable {
     FuzzTest fuzzTest =
         AnnotationSupport.findAnnotation(invocationContext.getExecutable(), FuzzTest.class).get();
-    FuzzTestExecutor.configureAndInstallAgent(extensionContext, fuzzTest.maxDuration());
+    FuzzTestExecutor.configureAndInstallAgent(
+        extensionContext, fuzzTest.maxDuration(), fuzzTest.maxExecutions());
     // Skip the invocation of the test method with the special arguments provided by
     // FuzzTestArgumentsProvider and start fuzzing instead.
     if (Utils.isMarkedInvocation(invocationContext)) {

src/main/java/com/code_intelligence/jazzer/junit/Utils.java

@@ -243,6 +243,9 @@ static boolean permissivelyParseBoolean(String value) {
    * allow for duration units longer than hours, so we can always prepend PT.
    */
   static long durationStringToSeconds(String duration) {
+    if (duration.isEmpty()) {
+      return 0;
+    }
     String isoDuration =
         "PT" + duration.replace("sec", "s").replace("min", "m").replace("hr", "h").replace(" ", "");
     return Duration.parse(isoDuration).getSeconds();

src/test/java/com/code_intelligence/jazzer/junit/UtilsTest.java

@@ -59,6 +59,8 @@ public class UtilsTest implements InvocationInterceptor {
 
   @Test
   void testDurationStringToSeconds() {
+    assertThat(durationStringToSeconds("")).isEqualTo(0);
+    assertThat(durationStringToSeconds("0s")).isEqualTo(0);
     assertThat(durationStringToSeconds("1m")).isEqualTo(60);
     assertThat(durationStringToSeconds("1min")).isEqualTo(60);
     assertThat(durationStringToSeconds("1h")).isEqualTo(60 * 60);