diff --git a/src/main/java/com/google/devtools/build/lib/BUILD b/src/main/java/com/google/devtools/build/lib/BUILD
index fa0c6af..1615493 100644
--- a/src/main/java/com/google/devtools/build/lib/BUILD
+++ b/src/main/java/com/google/devtools/build/lib/BUILD
@@ -1141,6 +1141,7 @@
         "//src/main/java/com/google/devtools/common/options",
         "//src/main/protobuf:crosstool_config_java_proto",
         "//src/main/protobuf:extra_actions_base_java_proto",
+        "//third_party:auto_value",
         "//third_party:guava",
         "//third_party:jsr305",
         "//third_party/protobuf:protobuf_java",
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntime.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntime.java
deleted file mode 100644
index 4c96dbe..0000000
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntime.java
+++ /dev/null
@@ -1,80 +0,0 @@
-// 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.bazel.rules.python;
-
-import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
-import com.google.devtools.build.lib.analysis.ConfiguredTarget;
-import com.google.devtools.build.lib.analysis.PrerequisiteArtifacts;
-import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
-import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
-import com.google.devtools.build.lib.analysis.RuleContext;
-import com.google.devtools.build.lib.analysis.RunfilesProvider;
-import com.google.devtools.build.lib.analysis.configuredtargets.RuleConfiguredTarget.Mode;
-import com.google.devtools.build.lib.collect.nestedset.NestedSet;
-import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
-import com.google.devtools.build.lib.syntax.Type;
-import com.google.devtools.build.lib.vfs.PathFragment;
-
-/**
- * Implementation for the {@code py_runtime} rule.
- */
-public final class BazelPyRuntime implements RuleConfiguredTargetFactory {
-
-  @Override
-  public ConfiguredTarget create(RuleContext ruleContext)
-      throws InterruptedException, RuleErrorException, ActionConflictException {
-    NestedSet<Artifact> files =
-        PrerequisiteArtifacts.nestedSet(ruleContext, "files", Mode.TARGET);
-    Artifact interpreter =
-        ruleContext.getPrerequisiteArtifact("interpreter", Mode.TARGET);
-    String interpreterPath =
-        ruleContext.attributes().get("interpreter_path", Type.STRING);
-
-    NestedSet<Artifact> all = NestedSetBuilder.<Artifact>stableOrder()
-        .addTransitive(files)
-        .build();
-
-    if (interpreter != null && !interpreterPath.isEmpty()) {
-      ruleContext.ruleError("interpreter and interpreter_path cannot be set at the same time.");
-    }
-
-    if (interpreter == null && interpreterPath.isEmpty()) {
-      ruleContext.ruleError("interpreter and interpreter_path cannot be empty at the same time.");
-    }
-
-    if (!interpreterPath.isEmpty() && !PathFragment.create(interpreterPath).isAbsolute()) {
-      ruleContext.attributeError("interpreter_path", "must be an absolute path.");
-    }
-
-    if (!interpreterPath.isEmpty() && !files.isEmpty()) {
-      ruleContext.ruleError("interpreter with an absolute path requires files to be empty.");
-    }
-
-    if (ruleContext.hasErrors()) {
-      return null;
-    }
-
-    BazelPyRuntimeProvider provider = BazelPyRuntimeProvider
-        .create(files, interpreter, interpreterPath);
-
-    return new RuleConfiguredTargetBuilder(ruleContext)
-        .addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
-        .setFilesToBuild(all)
-        .addProvider(BazelPyRuntimeProvider.class, provider)
-        .build();
-  }
-
-}
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeProvider.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeProvider.java
deleted file mode 100644
index e94afad..0000000
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeProvider.java
+++ /dev/null
@@ -1,44 +0,0 @@
-// 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.bazel.rules.python;
-
-import com.google.auto.value.AutoValue;
-import com.google.devtools.build.lib.actions.Artifact;
-import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
-import com.google.devtools.build.lib.collect.nestedset.NestedSet;
-import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
-import javax.annotation.Nullable;
-
-/** Information about the Python runtime used by the <code>py_*</code> rules. */
-@AutoValue
-@Immutable
-public abstract class BazelPyRuntimeProvider implements TransitiveInfoProvider {
-  public static BazelPyRuntimeProvider create(
-      NestedSet<Artifact> files,
-      @Nullable Artifact interpreter,
-      @Nullable String interpreterPath) {
-
-    return new AutoValue_BazelPyRuntimeProvider(files, interpreter, interpreterPath);
-  }
-
-  public abstract NestedSet<Artifact> files();
-
-  @Nullable
-  public abstract Artifact interpreter();
-
-  @Nullable
-  public abstract String interpreterPath();
-
-}
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeRule.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeRule.java
index 37cf1f6..44e064f 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeRule.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeRule.java
@@ -24,10 +24,11 @@
 import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
 import com.google.devtools.build.lib.packages.RuleClass;
+import com.google.devtools.build.lib.rules.python.PyRuntime;
 import com.google.devtools.build.lib.rules.python.PythonConfiguration;
 import com.google.devtools.build.lib.util.FileTypeSet;
 
-/** Rule definition for {@code python_runtime} */
+/** Rule definition for {@code py_runtime} */
 public final class BazelPyRuntimeRule implements RuleDefinition {
 
   @Override
@@ -38,24 +39,19 @@
         /* <!-- #BLAZE_RULE(py_runtime).ATTRIBUTE(files) -->
         The set of files comprising this Python runtime.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
-        .add(attr("files", LABEL_LIST)
-            .allowedFileTypes(FileTypeSet.ANY_FILE)
-            .mandatory())
+        .add(attr("files", LABEL_LIST).allowedFileTypes(FileTypeSet.ANY_FILE))
 
         /* <!-- #BLAZE_RULE(py_runtime).ATTRIBUTE(interpreter) -->
         The Python interpreter used in this runtime. Binary rules will be executed using this
         binary.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
-        .add(attr("interpreter", LABEL)
-            .allowedFileTypes(FileTypeSet.ANY_FILE)
-            .singleArtifact())
+        .add(attr("interpreter", LABEL).allowedFileTypes(FileTypeSet.ANY_FILE).singleArtifact())
 
         /* <!-- #BLAZE_RULE(py_runtime).ATTRIBUTE(interpreter_path) -->
         The absolute path of a Python interpreter. This attribute and interpreter attribute cannot
         be set at the same time.
         <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
         .add(attr("interpreter_path", STRING))
-
         .add(attr("output_licenses", LICENSE))
         .build();
   }
@@ -65,7 +61,7 @@
     return Metadata.builder()
         .name("py_runtime")
         .ancestors(BaseRuleClasses.BaseRule.class)
-        .factoryClass(BazelPyRuntime.class)
+        .factoryClass(PyRuntime.class)
         .build();
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonSemantics.java b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonSemantics.java
index b13d844..a7e0a28 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonSemantics.java
@@ -44,6 +44,7 @@
 import com.google.devtools.build.lib.rules.cpp.CcInfo;
 import com.google.devtools.build.lib.rules.python.PyCcLinkParamsProvider;
 import com.google.devtools.build.lib.rules.python.PyCommon;
+import com.google.devtools.build.lib.rules.python.PyRuntimeProvider;
 import com.google.devtools.build.lib.rules.python.PythonConfiguration;
 import com.google.devtools.build.lib.rules.python.PythonSemantics;
 import com.google.devtools.build.lib.util.FileTypeSet;
@@ -313,17 +314,17 @@
   }
 
   private static void addRuntime(RuleContext ruleContext, Runfiles.Builder builder) {
-    BazelPyRuntimeProvider provider = ruleContext.getPrerequisite(
-        ":py_interpreter", Mode.TARGET, BazelPyRuntimeProvider.class);
-    if (provider != null && provider.interpreter() != null) {
-      builder.addArtifact(provider.interpreter());
+    PyRuntimeProvider provider =
+        ruleContext.getPrerequisite(":py_interpreter", Mode.TARGET, PyRuntimeProvider.class);
+    if (provider != null && provider.isHermetic()) {
+      builder.addArtifact(provider.getInterpreter());
       // WARNING: we are adding the all Python runtime files here,
       // and it would fail if the filenames of them contain spaces.
       // Currently, we need to exclude them in py_runtime rules.
       // Possible files in Python runtime which contain spaces in filenames:
       // - https://github.com/pypa/setuptools/blob/master/setuptools/script%20(dev).tmpl
       // - https://github.com/pypa/setuptools/blob/master/setuptools/command/launcher%20manifest.xml
-      builder.addTransitiveArtifacts(provider.files());
+      builder.addTransitiveArtifacts(provider.getFiles());
     }
   }
 
@@ -333,20 +334,20 @@
 
     String pythonBinary;
 
-    BazelPyRuntimeProvider provider = ruleContext.getPrerequisite(
-        ":py_interpreter", Mode.TARGET, BazelPyRuntimeProvider.class);
+    PyRuntimeProvider provider =
+        ruleContext.getPrerequisite(":py_interpreter", Mode.TARGET, PyRuntimeProvider.class);
 
     if (provider != null) {
       // make use of py_runtime defined by --python_top
-      if (!provider.interpreterPath().isEmpty()) {
+      if (!provider.isHermetic()) {
         // absolute Python path in py_runtime
-        pythonBinary = provider.interpreterPath();
+        pythonBinary = provider.getInterpreterPath().getPathString();
       } else {
         // checked in Python interpreter in py_runtime
         PathFragment workspaceName =
             PathFragment.create(ruleContext.getRule().getPackage().getWorkspaceName());
         pythonBinary =
-            workspaceName.getRelative(provider.interpreter().getRunfilesPath()).getPathString();
+            workspaceName.getRelative(provider.getInterpreter().getRunfilesPath()).getPathString();
       }
     } else  {
       // make use of the Python interpreter in an absolute path
diff --git a/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntime.java b/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntime.java
new file mode 100644
index 0000000..74627e1
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntime.java
@@ -0,0 +1,72 @@
+// 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.rules.python;
+
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.PrerequisiteArtifacts;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.RunfilesProvider;
+import com.google.devtools.build.lib.analysis.configuredtargets.RuleConfiguredTarget.Mode;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.syntax.Type;
+import com.google.devtools.build.lib.vfs.PathFragment;
+
+/** Implementation for the {@code py_runtime} rule. */
+public final class PyRuntime implements RuleConfiguredTargetFactory {
+
+  @Override
+  public ConfiguredTarget create(RuleContext ruleContext) throws ActionConflictException {
+    NestedSet<Artifact> files =
+        PrerequisiteArtifacts.nestedSet(ruleContext, "files", Mode.TARGET);
+    Artifact interpreter = ruleContext.getPrerequisiteArtifact("interpreter", Mode.TARGET);
+    PathFragment interpreterPath =
+        PathFragment.create(ruleContext.attributes().get("interpreter_path", Type.STRING));
+
+    // Determine whether we're pointing to an in-build target (hermetic) or absolute system path
+    // (non-hermetic).
+    if ((interpreter == null) == interpreterPath.isEmpty()) {
+      ruleContext.ruleError(
+          "exactly one of the 'interpreter' or 'interpreter_path' attributes must be specified");
+    }
+    boolean hermetic = interpreter != null;
+    // Validate attributes.
+    if (!hermetic && !files.isEmpty()) {
+      ruleContext.ruleError("if 'interpreter_path' is given then 'files' must be empty");
+    }
+    if (!hermetic && !interpreterPath.isAbsolute()) {
+      ruleContext.attributeError("interpreter_path", "must be an absolute path.");
+    }
+
+    if (ruleContext.hasErrors()) {
+      return null;
+    }
+
+    PyRuntimeProvider provider =
+        hermetic
+            ? PyRuntimeProvider.create(files, interpreter, /*interpreterPath=*/ null)
+            : PyRuntimeProvider.create(/*files=*/ null, /*interpreter=*/ null, interpreterPath);
+
+    return new RuleConfiguredTargetBuilder(ruleContext)
+        .setFilesToBuild(files)
+        .addProvider(RunfilesProvider.class, RunfilesProvider.EMPTY)
+        .addProvider(PyRuntimeProvider.class, provider)
+        .build();
+  }
+
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntimeProvider.java b/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntimeProvider.java
new file mode 100644
index 0000000..c3230c0
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/python/PyRuntimeProvider.java
@@ -0,0 +1,60 @@
+// 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.rules.python;
+
+import com.google.auto.value.AutoValue;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.TransitiveInfoProvider;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import javax.annotation.Nullable;
+
+/** Information about the Python runtime used by the <code>py_*</code> rules. */
+@AutoValue
+@Immutable
+public abstract class PyRuntimeProvider implements TransitiveInfoProvider {
+
+  public static PyRuntimeProvider create(
+      @Nullable NestedSet<Artifact> files,
+      @Nullable Artifact interpreter,
+      @Nullable PathFragment interpreterPath) {
+    return new AutoValue_PyRuntimeProvider(files, interpreter, interpreterPath);
+  }
+
+  /**
+   * Returns whether this runtime is hermetic, i.e. represents an in-build interpreter as opposed to
+   * a system interpreter.
+   *
+   * <p>Hermetic runtimes have non-null values for {@link #getInterpreter} and {@link #getFiles},
+   * while non-hermetic runtimes have non-null {@link #getInterpreterPath}.
+   *
+   * <p>Note: Despite the name, it is still possible for a hermetic runtime to reference in-build
+   * files that have non-hermetic behavior. For example, {@link #getInterpreter} could reference a
+   * checked-in wrapper script that calls the system interpreter at execution time.
+   */
+  public boolean isHermetic() {
+    return getInterpreter() != null;
+  }
+
+  @Nullable
+  public abstract NestedSet<Artifact> getFiles();
+
+  @Nullable
+  public abstract Artifact getInterpreter();
+
+  @Nullable
+  public abstract PathFragment getInterpreterPath();
+}
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/BUILD b/src/test/java/com/google/devtools/build/lib/bazel/BUILD
index 6387494..b0e5f17 100644
--- a/src/test/java/com/google/devtools/build/lib/bazel/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/bazel/BUILD
@@ -48,7 +48,6 @@
         "//src/main/java/com/google/devtools/build/lib:core-workspace-rules",
         "//src/main/java/com/google/devtools/build/lib:events",
         "//src/main/java/com/google/devtools/build/lib:packages-internal",
-        "//src/main/java/com/google/devtools/build/lib:python-rules",
         "//src/main/java/com/google/devtools/build/lib:syntax",
         "//src/main/java/com/google/devtools/build/lib:util",
         "//src/main/java/com/google/devtools/build/lib/actions",
diff --git a/src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeTest.java b/src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeTest.java
deleted file mode 100644
index 1a7d460..0000000
--- a/src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPyRuntimeTest.java
+++ /dev/null
@@ -1,163 +0,0 @@
-// 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.bazel.rules.python;
-
-import static com.google.common.truth.Truth.assertThat;
-
-import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
-import com.google.devtools.build.lib.analysis.ConfiguredTarget;
-import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.ExpectedException;
-import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
-
-/**
- * Unit tests for {@link BazelPyRuntime}.
- */
-@RunWith(JUnit4.class)
-public final class BazelPyRuntimeTest extends BuildViewTestCase {
-
-  @Rule
-  public ExpectedException thrown = ExpectedException.none();
-
-  @Before
-  public final void setup() throws Exception {
-    scratch.file(
-      "py/BUILD",
-        "py_runtime(",
-        "    name='py-2.7',",
-        "    files = [",
-        "        'py-2.7/bin/python',",
-        "        'py-2.7/lib/libpython2.7.a',",
-        "     ],",
-        "    interpreter='py-2.7/bin/python',",
-        ")",
-        "",
-        "py_runtime(",
-        "    name='py-3.6',",
-        "    files = [],",
-        "    interpreter_path='/opt/pyenv/versions/3.6.0/bin/python',",
-        ")",
-        "",
-        "py_runtime(",
-        "    name='err-interpreter-and-path-both-set',",
-        "    files = [],",
-        "    interpreter='py-2.7/bin/python',",
-        "    interpreter_path='/opt/pyenv/versions/3.6.0/bin/python',",
-        ")",
-        "",
-        "py_runtime(",
-        "    name='err-interpreter-and-path-both-unset',",
-        "    files = [],",
-        ")",
-        "",
-        "py_runtime(",
-        "    name='err-path-not-absolute',",
-        "    files = [],",
-        "    interpreter_path='py-2.7/bin/python',",
-        ")",
-        "",
-        "py_runtime(",
-        "    name='err-non-empty-files-with-path-absolute',",
-        "    files = [",
-        "        'py-err/bin/python',",
-        "        'py-err/lib/libpython2.7.a',",
-        "     ],",
-        "    interpreter_path='/opt/pyenv/versions/3.6.0/bin/python',",
-        ")"
-    );
-
-  }
-
-  @Test
-  public void testCheckedInPyRuntime() throws Exception {
-    useConfiguration("--python_top=//py:py-2.7");
-    ConfiguredTarget target = getConfiguredTarget("//py:py-2.7");
-
-    assertThat(
-        ActionsTestUtil.prettyArtifactNames(
-            target.getProvider(BazelPyRuntimeProvider.class).files()))
-        .containsExactly("py/py-2.7/bin/python", "py/py-2.7/lib/libpython2.7.a");
-    assertThat(
-            target.getProvider(BazelPyRuntimeProvider.class).interpreter().getExecPathString())
-        .isEqualTo("py/py-2.7/bin/python");
-    assertThat(target.getProvider(BazelPyRuntimeProvider.class).interpreterPath())
-        .isEqualTo("");
-  }
-
-  @Test
-  public void testAbsolutePathPyRuntime() throws Exception {
-    useConfiguration("--python_top=//py:py-3.6");
-    ConfiguredTarget target = getConfiguredTarget("//py:py-3.6");
-
-    assertThat(
-        ActionsTestUtil.prettyArtifactNames(
-            target.getProvider(BazelPyRuntimeProvider.class).files()))
-        .isEmpty();
-    assertThat(
-        target.getProvider(BazelPyRuntimeProvider.class).interpreter())
-        .isNull();
-    assertThat(target.getProvider(BazelPyRuntimeProvider.class).interpreterPath())
-        .isEqualTo("/opt/pyenv/versions/3.6.0/bin/python");
-  }
-
-  @Test
-  public void testErrorWithInterpreterAndPathBothSet() throws Exception {
-    useConfiguration("--python_top=//py:err-interpreter-and-path-both-set");
-    try {
-      getConfiguredTarget("//py:err-interpreter-and-path-both-set");
-    } catch (Error e) {
-      assertThat(e.getMessage())
-          .contains("interpreter and interpreter_path cannot be set at the same time.");
-    }
-  }
-
-  @Test
-  public void testErrorWithInterpreterAndPathBothUnset() throws Exception {
-    useConfiguration("--python_top=//py:err-interpreter-and-path-both-unset");
-    try {
-      getConfiguredTarget("//py:err-interpreter-and-path-both-unset");
-    } catch (Error e) {
-      assertThat(e.getMessage())
-          .contains("interpreter and interpreter_path cannot be empty at the same time.");
-    }
-  }
-
-  @Test
-  public void testErrorWithPathNotAbsolute() throws Exception {
-    useConfiguration("--python_top=//py:err-path-not-absolute");
-    try {
-      getConfiguredTarget("//py:err-path-not-absolute");
-    } catch (Error e) {
-      assertThat(e.getMessage())
-          .contains("must be an absolute path.");
-    }
-  }
-
-  @Test
-  public void testPyRuntimeWithError() throws Exception {
-    useConfiguration("--python_top=//py:err-non-empty-files-with-path-absolute");
-    try {
-      getConfiguredTarget("//py:err-non-empty-files-with-path-absolute");
-    } catch (Error e) {
-      assertThat(e.getMessage())
-          .contains("interpreter with an absolute path requires files to be empty.");
-    }
-  }
-
-}
diff --git a/src/test/java/com/google/devtools/build/lib/rules/python/BazelPythonConfigurationTest.java b/src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonConfigurationTest.java
similarity index 94%
rename from src/test/java/com/google/devtools/build/lib/rules/python/BazelPythonConfigurationTest.java
rename to src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonConfigurationTest.java
index a6e4aad..cdb3223 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/python/BazelPythonConfigurationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/bazel/rules/python/BazelPythonConfigurationTest.java
@@ -12,14 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package com.google.devtools.build.lib.rules.python;
+package com.google.devtools.build.lib.bazel.rules.python;
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;
 
 import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
 import com.google.devtools.build.lib.analysis.util.ConfigurationTestCase;
-import com.google.devtools.build.lib.bazel.rules.python.BazelPythonConfiguration;
 import com.google.devtools.common.options.OptionsParsingException;
 import org.junit.Test;
 import org.junit.runner.RunWith;
diff --git a/src/test/java/com/google/devtools/build/lib/rules/python/BUILD b/src/test/java/com/google/devtools/build/lib/rules/python/BUILD
index 5edb30a..3df2ae7 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/python/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/rules/python/BUILD
@@ -12,11 +12,11 @@
 test_suite(
     name = "PythonTests",
     tests = [
-        ":BazelPythonConfigurationTest",
         ":PyBinaryConfiguredTargetTest",
         ":PyInfoTest",
         ":PyLibraryConfiguredTargetTest",
         ":PyProviderUtilsTest",
+        ":PyRuntimeTest",
         ":PyStructUtilsTest",
         ":PyTestConfiguredTargetTest",
         ":PythonConfigurationTest",
@@ -39,20 +39,6 @@
 )
 
 java_test(
-    name = "BazelPythonConfigurationTest",
-    srcs = ["BazelPythonConfigurationTest.java"],
-    deps = [
-        "//src/main/java/com/google/devtools/build/lib:bazel-rules",
-        "//src/main/java/com/google/devtools/build/lib:build-base",
-        "//src/main/java/com/google/devtools/common/options",
-        "//src/test/java/com/google/devtools/build/lib:analysis_testutil",
-        "//src/test/java/com/google/devtools/build/lib:testutil",
-        "//third_party:junit4",
-        "//third_party:truth",
-    ],
-)
-
-java_test(
     name = "PythonConfigurationTest",
     srcs = ["PythonConfigurationTest.java"],
     deps = [
@@ -67,6 +53,19 @@
     ],
 )
 
+java_test(
+    name = "PyRuntimeTest",
+    srcs = ["PyRuntimeTest.java"],
+    deps = [
+        "//src/main/java/com/google/devtools/build/lib:bazel-rules",
+        "//src/main/java/com/google/devtools/build/lib:python-rules",
+        "//src/test/java/com/google/devtools/build/lib:actions_testutil",
+        "//src/test/java/com/google/devtools/build/lib:analysis_testutil",
+        "//third_party:junit4",
+        "//third_party:truth",
+    ],
+)
+
 java_library(
     name = "PyBaseTestBase",
     srcs = ["PyBaseConfiguredTargetTestBase.java"],
diff --git a/src/test/java/com/google/devtools/build/lib/rules/python/PyRuntimeTest.java b/src/test/java/com/google/devtools/build/lib/rules/python/PyRuntimeTest.java
new file mode 100644
index 0000000..bf3b515
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/rules/python/PyRuntimeTest.java
@@ -0,0 +1,128 @@
+// Copyright 2019 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.rules.python;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
+import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@code py_runtime}. */
+@RunWith(JUnit4.class)
+public class PyRuntimeTest extends BuildViewTestCase {
+
+  @Before
+  public final void setUpPython() throws Exception {
+    analysisMock.pySupport().setup(mockToolsConfig);
+  }
+
+  @Test
+  public void hermeticRuntime() throws Exception {
+    scratch.file(
+        "pkg/BUILD",
+        "py_runtime(",
+        "    name = 'myruntime',",
+        "    files = [':myfile'],",
+        "    interpreter = ':myinterpreter',",
+        ")");
+    PyRuntimeProvider info =
+        getConfiguredTarget("//pkg:myruntime").getProvider(PyRuntimeProvider.class);
+
+    assertThat(info.isHermetic()).isTrue();
+    assertThat(info.getInterpreterPath()).isNull();
+    assertThat(info.getInterpreter().getExecPathString()).isEqualTo("pkg/myinterpreter");
+    assertThat(ActionsTestUtil.baseArtifactNames(info.getFiles())).containsExactly("myfile");
+  }
+
+  @Test
+  public void nonhermeticRuntime() throws Exception {
+    scratch.file(
+        "pkg/BUILD",
+        "py_runtime(",
+        "    name = 'myruntime',",
+        "    interpreter_path = '/system/interpreter',",
+        ")");
+    PyRuntimeProvider info =
+        getConfiguredTarget("//pkg:myruntime").getProvider(PyRuntimeProvider.class);
+
+    assertThat(info.isHermetic()).isFalse();
+    assertThat(info.getInterpreterPath().getPathString()).isEqualTo("/system/interpreter");
+    assertThat(info.getInterpreter()).isNull();
+    assertThat(info.getFiles()).isNull();
+  }
+
+  @Test
+  public void cannotUseBothInterpreterAndPath() throws Exception {
+    reporter.removeHandler(failFastHandler);
+    scratch.file(
+        "pkg/BUILD",
+        "py_runtime(",
+        "    name = 'myruntime',",
+        "    interpreter = ':myinterpreter',",
+        "    interpreter_path = '/system/interpreter',",
+        ")");
+    getConfiguredTarget("//pkg:myruntime");
+
+    assertContainsEvent(
+        "exactly one of the 'interpreter' or 'interpreter_path' attributes must be specified");
+  }
+
+  @Test
+  public void mustUseEitherInterpreterOrPath() throws Exception {
+    reporter.removeHandler(failFastHandler);
+    scratch.file(
+        "pkg/BUILD", //
+        "py_runtime(",
+        "    name = 'myruntime',",
+        ")");
+    getConfiguredTarget("//pkg:myruntime");
+
+    assertContainsEvent(
+        "exactly one of the 'interpreter' or 'interpreter_path' attributes must be specified");
+  }
+
+  @Test
+  public void interpreterPathMustBeAbsolute() throws Exception {
+    reporter.removeHandler(failFastHandler);
+    scratch.file(
+        "pkg/BUILD",
+        "py_runtime(",
+        "    name = 'myruntime',",
+        "    interpreter_path = 'some/relative/path',",
+        ")");
+    getConfiguredTarget("//pkg:myruntime");
+
+    assertContainsEvent("must be an absolute path");
+  }
+
+  @Test
+  public void cannotSpecifyFilesForNonhermeticRuntime() throws Exception {
+    reporter.removeHandler(failFastHandler);
+    scratch.file(
+        "pkg/BUILD",
+        "py_runtime(",
+        "    name = 'myruntime',",
+        "    files = [':myfile'],",
+        "    interpreter_path = '/system/interpreter',",
+        ")");
+    getConfiguredTarget("//pkg:myruntime");
+
+    assertContainsEvent("if 'interpreter_path' is given then 'files' must be empty");
+  }
+}