Add hook to process SkyframeExecutor in tests. Also add sentinel exception to indicate unserializability, improve error message in Path when serialization fails, and add some test-only methods to SkyframeExecutor and PackageFactory.

PiperOrigin-RevId: 162993806
diff --git a/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java b/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
index c97af34e..829e1c8 100644
--- a/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
+++ b/src/test/java/com/google/devtools/build/lib/pkgcache/IncrementalLoadingTest.java
@@ -41,6 +41,7 @@
 import com.google.devtools.build.lib.syntax.GlobList;
 import com.google.devtools.build.lib.syntax.SkylarkSemanticsOptions;
 import com.google.devtools.build.lib.testutil.ManualClock;
+import com.google.devtools.build.lib.testutil.TestConstants;
 import com.google.devtools.build.lib.util.BlazeClock;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
@@ -484,6 +485,7 @@
               BazelSkyframeExecutorConstants.CROSS_REPOSITORY_LABEL_VIOLATION_STRATEGY,
               BazelSkyframeExecutorConstants.BUILD_FILES_BY_PRIORITY,
               BazelSkyframeExecutorConstants.ACTION_ON_IO_EXCEPTION_READING_BUILD_FILE);
+      TestConstants.processSkyframeExecutorForTesting(skyframeExecutor);
       PackageCacheOptions packageCacheOptions = Options.getDefaults(PackageCacheOptions.class);
       packageCacheOptions.defaultVisibility = ConstantRuleVisibility.PUBLIC;
       packageCacheOptions.showLoadingProgress = true;