Remove assumption from test that /a and /b don't exist.

The updated test cases in the InMemoryFileSystemTest make
the assumption that /a and /b are not prefixes of the
InMemoryFilesystemTest.workingDir field. This is not safe
and thus use a randomly generated directory name instead
of a hardcoded one.

PiperOrigin-RevId: 188872604

src/test/java/com/google/devtools/build/lib/vfs/inmemoryfs/InMemoryFileSystemTest.java

@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.vfs.inmemoryfs;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
 
 import com.google.common.collect.Lists;
 import com.google.devtools.build.lib.clock.BlazeClock;
@@ -28,6 +29,7 @@
 import java.io.OutputStream;
 import java.nio.charset.Charset;
 import java.util.Collection;
+import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -384,25 +386,34 @@ public void runTest() throws Exception {
 
   @Test
   public void testEloop() throws Exception {
-    Path a = testFS.getPath("/a");
-    Path b = testFS.getPath("/b");
-    a.createSymbolicLink(PathFragment.create("b"));
-    b.createSymbolicLink(PathFragment.create("a"));
+    // The test assumes that aName and bName is not a prefix of the workingDir.
+    String aName = "/" + UUID.randomUUID();
+    String bName = "/" + UUID.randomUUID();
+
+    Path a = testFS.getPath(aName);
+    Path b = testFS.getPath(bName);
+    a.createSymbolicLink(PathFragment.create(bName));
+    b.createSymbolicLink(PathFragment.create(aName));
     try {
       a.stat();
+      fail("Expected IOException");
     } catch (IOException e) {
-      assertThat(e).hasMessage("/a (Too many levels of symbolic links)");
+      assertThat(e).hasMessage(aName + " (Too many levels of symbolic links)");
     }
   }
 
   @Test
   public void testEloopSelf() throws Exception {
-    Path a = testFS.getPath("/a");
-    a.createSymbolicLink(PathFragment.create("a"));
+    // The test assumes that aName is not a prefix of the workingDir.
+    String aName = "/" + UUID.randomUUID();
+
+    Path a = testFS.getPath(aName);
+    a.createSymbolicLink(PathFragment.create(aName));
     try {
       a.stat();
+      fail("Expected IOException");
     } catch (IOException e) {
-      assertThat(e).hasMessage("/a (Too many levels of symbolic links)");
+      assertThat(e).hasMessage(aName + " (Too many levels of symbolic links)");
     }
   }
 }