Add CEL expression to CelTestContext

PiperOrigin-RevId: 773272797

Author: ChinmayMadeshi

testing/src/main/java/dev/cel/testing/testrunner/CelTestContext.java

@@ -79,6 +79,13 @@ public abstract class CelTestContext {
    */
   public abstract ResultMatcher resultMatcher();
 
+  /**
+   * The CEL expression to be tested. Could be a raw CEL expression or a policy/cel file path.
+   *
+   * <p>This expression is used incase the expression is not provided via the build macro.
+   */
+  public abstract Optional<String> celExpression();
+
   /** Returns a builder for {@link CelTestContext} with the current instance's values. */
   public abstract Builder toBuilder();
 
@@ -107,6 +114,8 @@ public abstract Builder setCelLateFunctionBindings(
 
     public abstract Builder setResultMatcher(ResultMatcher resultMatcher);
 
+    public abstract Builder setCelExpression(String celExpression);
+
     public abstract CelTestContext build();
   }
 }

testing/src/main/java/dev/cel/testing/testrunner/TestRunnerLibrary.java

@@ -77,7 +77,20 @@ public final class TestRunnerLibrary {
    */
   public static void runTest(CelTestCase testCase, CelTestContext celTestContext) throws Exception {
     String celExpression = System.getProperty(CEL_EXPR_SYSTEM_PROPERTY);
-    CelExprFileSource celExprFileSource = CelExprFileSource.fromFile(celExpression);
+    CelExprFileSource celExprFileSource;
+    if (celExpression == null) {
+      celExprFileSource =
+          celTestContext
+              .celExpression()
+              .map(CelExprFileSource::fromFile)
+              .orElseThrow(
+                  () ->
+                      new IllegalArgumentException(
+                          "No cel expression provided in the test case or via cel_test build"
+                              + " macro."));
+    } else {
+      celExprFileSource = CelExprFileSource.fromFile(celExpression);
+    }
     evaluateTestCase(testCase, celTestContext, celExprFileSource);
   }
 

testing/src/test/java/dev/cel/testing/testrunner/TestRunnerLibraryTest.java

@@ -55,6 +55,25 @@ public void runPolicyTest_simpleBooleanOutput() throws Exception {
         simpleOutputTestCase, CelTestContext.newBuilder().build(), celExprFileSource);
   }
 
+  @Test
+  public void evaluateTestCase_simpleBooleanOutput() throws Exception {
+    CelTestCase simpleOutputTestCase =
+        CelTestCase.newBuilder()
+            .setName("simple_output_test_case")
+            .setDescription("simple_output_test_case_description")
+            .setInput(CelTestSuite.CelTestSection.CelTestCase.Input.ofBindings(ImmutableMap.of()))
+            .setOutput(CelTestSuite.CelTestSection.CelTestCase.Output.ofResultValue(false))
+            .build();
+
+    TestRunnerLibrary.runTest(
+        simpleOutputTestCase,
+        CelTestContext.newBuilder()
+            .setCelExpression(
+                TestUtil.getSrcDir()
+                    + "/google3/third_party/java/cel/testing/src/test/java/dev/cel/testing/testrunner/resources/empty_policy.yaml")
+            .build());
+  }
+
   @Test
   public void runPolicyTest_outputMismatch_failureAssertion() throws Exception {
     CelTestCase simpleOutputTestCase =