diff --git a/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
new file mode 100644
index 0000000..fdfa655
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+++ b/src/test/java/com/google/devtools/build/lib/exec/SpawnInputExpanderTest.java
@@ -0,0 +1,242 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// 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 com.google.devtools.build.lib.exec;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.Maps;
+import com.google.devtools.build.lib.actions.ActionInput;
+import com.google.devtools.build.lib.actions.ActionInputFileCache;
+import com.google.devtools.build.lib.actions.ActionInputHelper;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.EmptyRunfilesSupplier;
+import com.google.devtools.build.lib.actions.Root;
+import com.google.devtools.build.lib.actions.RunfilesSupplier;
+import com.google.devtools.build.lib.analysis.Runfiles;
+import com.google.devtools.build.lib.analysis.RunfilesSupplierImpl;
+import com.google.devtools.build.lib.vfs.FileSystem;
+import com.google.devtools.build.lib.vfs.FileSystemUtils;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.Mockito;
+
+/**
+ * Tests for {@link SpawnInputExpander}.
+ */
+@RunWith(JUnit4.class)
+public class SpawnInputExpanderTest {
+  private FileSystem fs;
+  private SpawnInputExpander expander;
+  private Map<PathFragment, ActionInput> inputMappings;
+
+  @Before
+  public final void createSpawnInputExpander() throws Exception  {
+    fs = new InMemoryFileSystem();
+    expander = new SpawnInputExpander(/*strict=*/true);
+    inputMappings = Maps.newHashMap();
+  }
+
+  private void scratchFile(String file, String... lines) throws Exception {
+    Path path = fs.getPath(file);
+    FileSystemUtils.createDirectoryAndParents(path.getParentDirectory());
+    FileSystemUtils.writeLinesAs(path, StandardCharsets.UTF_8, lines);
+  }
+
+  @Test
+  public void testEmptyRunfiles() throws Exception {
+    RunfilesSupplier supplier = EmptyRunfilesSupplier.INSTANCE;
+    expander.addRunfilesToInputs(inputMappings, supplier, null);
+    assertThat(inputMappings).isEmpty();
+  }
+
+  @Test
+  public void testRunfilesSingleFile() throws Exception {
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact)).thenReturn(true);
+
+    expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+    assertThat(inputMappings).hasSize(1);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("runfiles/workspace/dir/file"), artifact);
+  }
+
+  @Test
+  public void testRunfilesDirectoryStrict() throws Exception {
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact)).thenReturn(false);
+
+    try {
+      expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+      fail();
+    } catch (IOException expected) {
+      assertThat(expected.getMessage().contains("Not a file: /root/dir/file")).isTrue();
+    }
+  }
+
+  @Test
+  public void testRunfilesDirectoryNonStrict() throws Exception {
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace").addArtifact(artifact).build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact)).thenReturn(false);
+
+    expander = new SpawnInputExpander(/*strict=*/false);
+    expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+    assertThat(inputMappings).hasSize(1);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("runfiles/workspace/dir/file"), artifact);
+  }
+
+  @Test
+  public void testRunfilesTwoFiles() throws Exception {
+    Artifact artifact1 =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Artifact artifact2 =
+        new Artifact(fs.getPath("/root/dir/baz"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace")
+        .addArtifact(artifact1)
+        .addArtifact(artifact2)
+        .build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact1)).thenReturn(true);
+    Mockito.when(mockCache.isFile(artifact2)).thenReturn(true);
+
+    expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+    assertThat(inputMappings).hasSize(2);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("runfiles/workspace/dir/file"), artifact1);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("runfiles/workspace/dir/baz"), artifact2);
+  }
+
+  @Test
+  public void testRunfilesSymlink() throws Exception {
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace")
+        .addSymlink(new PathFragment("symlink"), artifact).build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact)).thenReturn(true);
+
+    expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+    assertThat(inputMappings).hasSize(1);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("runfiles/workspace/symlink"), artifact);
+  }
+
+  @Test
+  public void testRunfilesRootSymlink() throws Exception {
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/dir/file"), Root.asSourceRoot(fs.getPath("/root")));
+    Runfiles runfiles = new Runfiles.Builder("workspace")
+        .addRootSymlink(new PathFragment("symlink"), artifact).build();
+    RunfilesSupplier supplier = new RunfilesSupplierImpl(new PathFragment("runfiles"), runfiles);
+    ActionInputFileCache mockCache = Mockito.mock(ActionInputFileCache.class);
+    Mockito.when(mockCache.isFile(artifact)).thenReturn(true);
+
+    expander.addRunfilesToInputs(inputMappings, supplier, mockCache);
+    assertThat(inputMappings).hasSize(2);
+    assertThat(inputMappings).containsEntry(new PathFragment("runfiles/symlink"), artifact);
+    // If there's no other entry, Runfiles adds an empty file in the workspace to make sure the
+    // directory gets created.
+    assertThat(inputMappings)
+        .containsEntry(
+            new PathFragment("runfiles/workspace/.runfile"), SpawnInputExpander.EMPTY_FILE);
+  }
+
+  @Test
+  public void testEmptyManifest() throws Exception {
+    // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
+    scratchFile("/root/_foo/MANIFEST");
+
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/foo"), Root.asSourceRoot(fs.getPath("/root")));
+    expander.parseFilesetManifest(inputMappings, artifact, "workspace");
+    assertThat(inputMappings).isEmpty();
+  }
+
+  @Test
+  public void testManifestWithSingleFile() throws Exception {
+    // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
+    scratchFile(
+        "/root/_foo/MANIFEST",
+        "workspace/bar /dir/file",
+        "<some digest>");
+
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/foo"), Root.asSourceRoot(fs.getPath("/root")));
+    expander.parseFilesetManifest(inputMappings, artifact, "workspace");
+    assertThat(inputMappings).hasSize(1);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("foo/bar"), ActionInputHelper.fromPath("/dir/file"));
+  }
+
+  @Test
+  public void testManifestWithTwoFiles() throws Exception {
+    // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
+    scratchFile(
+        "/root/_foo/MANIFEST",
+        "workspace/bar /dir/file",
+        "<some digest>",
+        "workspace/baz /dir/file",
+        "<some digest>");
+
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/foo"), Root.asSourceRoot(fs.getPath("/root")));
+    expander.parseFilesetManifest(inputMappings, artifact, "workspace");
+    assertThat(inputMappings).hasSize(2);
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("foo/bar"), ActionInputHelper.fromPath("/dir/file"));
+    assertThat(inputMappings)
+        .containsEntry(new PathFragment("foo/baz"), ActionInputHelper.fromPath("/dir/file"));
+  }
+
+  @Test
+  public void testManifestWithDirectory() throws Exception {
+    // See AnalysisUtils for the mapping from "foo" to "_foo/MANIFEST".
+    scratchFile(
+        "/root/_foo/MANIFEST",
+        "workspace/bar /some",
+        "<some digest>");
+
+    Artifact artifact =
+        new Artifact(fs.getPath("/root/foo"), Root.asSourceRoot(fs.getPath("/root")));
+    expander.parseFilesetManifest(inputMappings, artifact, "workspace");
+    assertThat(inputMappings).hasSize(1);
+    assertThat(inputMappings)
+        .containsEntry(
+            new PathFragment("foo/bar"), ActionInputHelper.fromPath("/some"));
+  }
+}