Remove superfluous test singletons.

RELNOTES: None.
PiperOrigin-RevId: 267320407
diff --git a/src/test/java/com/google/devtools/build/lib/vfs/FileSystemsTest.java b/src/test/java/com/google/devtools/build/lib/vfs/FileSystemsTest.java
index 0fad961..969f11d 100644
--- a/src/test/java/com/google/devtools/build/lib/vfs/FileSystemsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/vfs/FileSystemsTest.java
@@ -27,19 +27,7 @@
 public class FileSystemsTest {
 
   @Test
-  public void testFileSystemsCreatesOnlyOneDefaultNative() {
-    assertThat(FileSystems.getNativeFileSystem())
-        .isSameInstanceAs(FileSystems.getNativeFileSystem());
-  }
-
-  @Test
-  public void testFileSystemsCreatesOnlyOneDefaultJavaIo() {
-    assertThat(FileSystems.getJavaIoFileSystem())
-        .isSameInstanceAs(FileSystems.getJavaIoFileSystem());
-  }
-
-  @Test
-  public void testFileSystemsCanSwitchDefaults() {
+  public void testFileSystems() {
     assertThat(FileSystems.getJavaIoFileSystem())
         .isNotSameInstanceAs(FileSystems.getNativeFileSystem());
   }