Introduce "minimal" test reporter (#1563)

docs/modules/pkl-cli/pages/index.adoc

@@ -546,6 +546,15 @@ When enabled, test failures will show intermediate values in the assertion expre
 Use `--no-power-assertions` to disable this feature if you prefer simpler output.
 ====
 
+[[test-reporter]]
+.--test-reporter
+[%collapsible]
+====
+Default: `spec` +
+Example: `--test-reporter minimal` +
+Which test reporter to use for CLI output. Possible values are `spec` and `minimal`.
+====
+
 This command also takes <<common-options, common options>>.
 
 [[command-run]]
@@ -667,6 +676,14 @@ Force generation of expected examples. +
 The old expected files will be deleted if present.
 ====
 
+.--test-reporter
+[%collapsible]
+====
+Default: `spec` +
+Example: `--test-reporter minimal` +
+Which test reporter to use for CLI output. Possible values are `spec` and `minimal`.
+====
+
 This command also takes <<common-options,common options>>.
 
 [[command-project-resolve]]

docs/modules/pkl-gradle/pages/index.adoc

@@ -322,6 +322,15 @@ Default: `false` +
 Whether to ignore expected example files and generate them again.
 ====
 
+[[test-reporter]]
+.test-reporter: Property<String>
+[%collapsible]
+====
+Default: `"spec"` +
+Example: `reporter = "minimal"` +
+Which test reporter to use for CLI output. Possible values are `"spec"` and `"minimal"`.
+====
+
 [[power-assertions-test]]
 .powerAssertions: Property<Boolean>
 [%collapsible]
@@ -677,6 +686,14 @@ Default: `false` +
 Whether to ignore expected example files and generate them again.
 ====
 
+.test-reporter: Property<String>
+[%collapsible]
+====
+Default: `"spec"` +
+Example: `reporter = "minimal"` +
+Which test reporter to use for CLI output. Possible values are `"spec"` and `"minimal"`.
+====
+
 Common properties:
 
 include::../partials/gradle-common-properties.adoc[]

pkl-cli/src/main/kotlin/org/pkl/cli/CliTestRunner.kt

@@ -15,6 +15,7 @@
  */
 package org.pkl.cli
 
+import java.io.StringWriter
 import java.io.Writer
 import org.pkl.commons.cli.*
 import org.pkl.core.Closeables
@@ -22,8 +23,9 @@ import org.pkl.core.EvaluatorBuilder
 import org.pkl.core.ModuleSource.uri
 import org.pkl.core.PklException
 import org.pkl.core.TestResults
-import org.pkl.core.stdlib.test.report.JUnitReport
-import org.pkl.core.stdlib.test.report.SimpleReport
+import org.pkl.core.stdlib.test.report.JUnitReporter
+import org.pkl.core.stdlib.test.report.MinimalReporter
+import org.pkl.core.stdlib.test.report.SpecReporter
 import org.pkl.core.util.ErrorMessages
 
 class CliTestRunner
@@ -64,13 +66,15 @@ constructor(
       var failed = false
       var isExampleWrittenFailure = true
       val moduleNames = mutableSetOf<String>()
-      val reporter = SimpleReport(useColor)
+      val reporter =
+        when (testOptions.reporter) {
+          TestReporter.SPEC -> SpecReporter(useColor)
+          TestReporter.MINIMAL -> MinimalReporter(useColor)
+        }
       val allTestResults = mutableListOf<TestResults>()
 
       val junitDir = testOptions.junitDir
-      if (junitDir != null) {
-        junitDir.toFile().mkdirs()
-      }
+      junitDir?.toFile()?.mkdirs()
 
       for ((idx, moduleUri) in sources.withIndex()) {
         try {
@@ -80,8 +84,11 @@ constructor(
             failed = results.failed()
             isExampleWrittenFailure = results.isExampleWrittenFailure.and(isExampleWrittenFailure)
           }
-          reporter.report(results, consoleWriter)
-          if (sources.size > 1 && idx != sources.size - 1) {
+          val tmpWriter = StringWriter()
+          reporter.report(results, tmpWriter)
+          val report = tmpWriter.toString()
+          consoleWriter.write(report)
+          if (report.isNotEmpty() && sources.size > 1 && idx != sources.size - 1) {
             consoleWriter.append('\n')
           }
           consoleWriter.flush()
@@ -101,7 +108,7 @@ constructor(
             moduleNames += moduleName
 
             if (!testOptions.junitAggregateReports) {
-              JUnitReport().reportToPath(results, junitDir.resolve(moduleName))
+              JUnitReporter().reportToPath(results, junitDir.resolve(moduleName))
             }
           }
         } catch (ex: Exception) {
@@ -119,7 +126,7 @@ constructor(
       }
       if (testOptions.junitAggregateReports && junitDir != null) {
         val fileName = "${testOptions.junitAggregateSuiteName}.xml"
-        JUnitReport(testOptions.junitAggregateSuiteName)
+        JUnitReporter(testOptions.junitAggregateSuiteName)
           .summarizeToPath(allTestResults, junitDir.resolve(fileName))
       }
       consoleWriter.append('\n')

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/CliTestOptions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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.
@@ -22,4 +22,5 @@ class CliTestOptions(
   val overwrite: Boolean = false,
   val junitAggregateReports: Boolean = false,
   val junitAggregateSuiteName: String = "pkl-tests",
+  val reporter: TestReporter = TestReporter.SPEC,
 )

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/TestReporter.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright © 2026 Apple Inc. and the Pkl project 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
+ *
+ *     https://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 org.pkl.commons.cli
+
+enum class TestReporter {
+  SPEC,
+  MINIMAL,
+}

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/commands/TestOptions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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.
@@ -19,9 +19,11 @@ import com.github.ajalt.clikt.parameters.groups.OptionGroup
 import com.github.ajalt.clikt.parameters.options.default
 import com.github.ajalt.clikt.parameters.options.flag
 import com.github.ajalt.clikt.parameters.options.option
+import com.github.ajalt.clikt.parameters.types.enum
 import com.github.ajalt.clikt.parameters.types.path
 import java.nio.file.Path
 import org.pkl.commons.cli.CliTestOptions
+import org.pkl.commons.cli.TestReporter
 
 class TestOptions : OptionGroup() {
   private val junitReportDir: Path? by
@@ -51,7 +53,19 @@ class TestOptions : OptionGroup() {
   private val overwrite: Boolean by
     option(names = arrayOf("--overwrite"), help = "Force generation of expected examples.").flag()
 
+  private val reporter: TestReporter by
+    option(names = arrayOf("--test-reporter"), help = "Which test reporter to use for CLI output.")
+      .enum<TestReporter> { it.name.lowercase() }
+      .single()
+      .default(TestReporter.SPEC)
+
   val cliTestOptions: CliTestOptions by lazy {
-    CliTestOptions(junitReportDir, overwrite, junitAggregateReports, junitAggregateSuiteName)
+    CliTestOptions(
+      junitReportDir,
+      overwrite,
+      junitAggregateReports,
+      junitAggregateSuiteName,
+      reporter,
+    )
   }
 }

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/BaseReporter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2026 Apple Inc. and the Pkl project 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.
@@ -24,41 +24,21 @@ import java.util.Locale;
 import java.util.stream.Collectors;
 import org.pkl.core.TestResults;
 import org.pkl.core.TestResults.TestResult;
-import org.pkl.core.TestResults.TestSectionResults;
 import org.pkl.core.util.AnsiStringBuilder;
 import org.pkl.core.util.AnsiStringBuilder.AnsiCode;
 import org.pkl.core.util.AnsiTheme;
 import org.pkl.core.util.StringUtils;
 
-public final class SimpleReport implements TestReport {
+public abstract class BaseReporter implements TestReporter {
+  protected static final String passingMark = "✔ ";
+  protected static final String failingMark = "✘ ";
 
-  private static final String passingMark = "✔ ";
-  private static final String failingMark = "✘ ";
+  protected final boolean useColor;
 
-  private final boolean useColor;
-
-  public SimpleReport(boolean useColor) {
+  public BaseReporter(boolean useColor) {
     this.useColor = useColor;
   }
 
-  @Override
-  public void report(TestResults results, Writer writer) throws IOException {
-    var builder = new AnsiStringBuilder(useColor);
-
-    builder.append("module ").append(results.moduleName()).append('\n');
-
-    if (results.error() != null) {
-      var rendered = results.error().exception().getMessage();
-      appendPadded(builder, rendered, "  ");
-      builder.append('\n');
-    } else {
-      reportResults(results.facts(), builder);
-      reportResults(results.examples(), builder);
-    }
-
-    writer.append(builder.toString());
-  }
-
   @Override
   public void summarize(List<TestResults> allTestResults, Writer writer) throws IOException {
     var totalTests = 0;
@@ -91,16 +71,7 @@ public final class SimpleReport implements TestReport {
     writer.append(builder.toString());
   }
 
-  private void reportResults(TestSectionResults section, AnsiStringBuilder builder) {
-    if (!section.results().isEmpty()) {
-      builder.append("  ").append(section.name()).append('\n');
-      StringUtils.joinToStringBuilder(
-          builder, section.results(), "\n", res -> reportResult(res, builder));
-      builder.append('\n');
-    }
-  }
-
-  private void reportResult(TestResult result, AnsiStringBuilder builder) {
+  protected void reportResult(TestResult result, AnsiStringBuilder builder) {
     builder.append("    ");
 
     if (result.isExampleWritten()) {
@@ -129,7 +100,7 @@ public final class SimpleReport implements TestReport {
     }
   }
 
-  private static void appendPadded(AnsiStringBuilder builder, String lines, String padding) {
+  protected static void appendPadded(AnsiStringBuilder builder, String lines, String padding) {
     StringUtils.joinToStringBuilder(
         builder,
         lines.lines().collect(Collectors.toList()),

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/JUnitReporter.java

@@ -37,15 +37,15 @@ import org.pkl.core.stdlib.PklConverter;
 import org.pkl.core.stdlib.xml.RendererNodes.Renderer;
 import org.pkl.core.util.EconomicMaps;
 
-public final class JUnitReport implements TestReport {
+public final class JUnitReporter implements TestReporter {
 
   private final String aggregateSuiteName;
 
-  public JUnitReport(String aggregateSuiteName) {
+  public JUnitReporter(String aggregateSuiteName) {
     this.aggregateSuiteName = aggregateSuiteName;
   }
 
-  public JUnitReport() {
+  public JUnitReporter() {
     this("");
   }
 

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/MinimalReporter.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright © 2026 Apple Inc. and the Pkl project 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
+ *
+ *     https://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 org.pkl.core.stdlib.test.report;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.util.List;
+import org.pkl.core.TestResults;
+import org.pkl.core.TestResults.TestResult;
+import org.pkl.core.TestResults.TestSectionResults;
+import org.pkl.core.util.AnsiStringBuilder;
+import org.pkl.core.util.StringUtils;
+
+/** Minimal reporter. Only reports failures and errors. */
+public final class MinimalReporter extends BaseReporter {
+
+  public MinimalReporter(boolean useColor) {
+    super(useColor);
+  }
+
+  @Override
+  public void report(TestResults results, Writer writer) throws IOException {
+    var builder = new AnsiStringBuilder(useColor);
+
+    if (results.error() != null) {
+      builder.append("module ").append(results.moduleName()).append('\n');
+
+      var rendered = results.error().exception().getMessage();
+      appendPadded(builder, rendered, "  ");
+      builder.append('\n');
+    } else {
+      var factFailures = results.facts().results().stream().filter(TestResult::isFailure).toList();
+      var exampleFailures =
+          results.examples().results().stream().filter(TestResult::isFailure).toList();
+      if (!factFailures.isEmpty() || !exampleFailures.isEmpty()) {
+        builder.append("module ").append(results.moduleName()).append('\n');
+
+        reportResults(results.facts(), factFailures, builder);
+        reportResults(results.examples(), exampleFailures, builder);
+      }
+    }
+
+    writer.append(builder.toString());
+  }
+
+  private void reportResults(
+      TestSectionResults section, List<TestResults.TestResult> results, AnsiStringBuilder builder) {
+    if (!results.isEmpty()) {
+      builder.append("  ").append(section.name()).append('\n');
+      StringUtils.joinToStringBuilder(builder, results, "\n", res -> reportResult(res, builder));
+      builder.append('\n');
+    }
+  }
+}

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/SpecReporter.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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
+ *
+ *     https://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 org.pkl.core.stdlib.test.report;
+
+import java.io.IOException;
+import java.io.Writer;
+import org.pkl.core.TestResults;
+import org.pkl.core.TestResults.TestSectionResults;
+import org.pkl.core.util.AnsiStringBuilder;
+import org.pkl.core.util.StringUtils;
+
+public final class SpecReporter extends BaseReporter {
+
+  public SpecReporter(boolean useColor) {
+    super(useColor);
+  }
+
+  @Override
+  public void report(TestResults results, Writer writer) throws IOException {
+    var builder = new AnsiStringBuilder(useColor);
+
+    builder.append("module ").append(results.moduleName()).append('\n');
+
+    if (results.error() != null) {
+      var rendered = results.error().exception().getMessage();
+      appendPadded(builder, rendered, "  ");
+      builder.append('\n');
+    } else {
+      reportResults(results.facts(), builder);
+      reportResults(results.examples(), builder);
+    }
+
+    writer.append(builder.toString());
+  }
+
+  private void reportResults(TestSectionResults section, AnsiStringBuilder builder) {
+    if (!section.results().isEmpty()) {
+      builder.append("  ").append(section.name()).append('\n');
+      StringUtils.joinToStringBuilder(
+          builder, section.results(), "\n", res -> reportResult(res, builder));
+      builder.append('\n');
+    }
+  }
+}

pkl-core/src/main/java/org/pkl/core/stdlib/test/report/TestReporter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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.
@@ -25,7 +25,7 @@ import org.pkl.core.PklBugException;
 import org.pkl.core.TestResults;
 import org.pkl.core.util.StringBuilderWriter;
 
-public interface TestReport {
+public interface TestReporter {
 
   void report(TestResults results, Writer writer) throws IOException;
 

pkl-core/src/test/kotlin/org/pkl/core/stdlib/MinimalReportTest.kt

@@ -0,0 +1,158 @@
+/*
+ * Copyright © 2026 Apple Inc. and the Pkl project 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
+ *
+ *     https://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 org.pkl.core.stdlib
+
+import java.io.StringWriter
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.pkl.core.TestResults
+import org.pkl.core.TestResults.TestResult
+import org.pkl.core.TestResults.TestSectionResults
+import org.pkl.core.stdlib.test.report.MinimalReporter
+
+class MinimalReportTest {
+
+  @Test
+  fun `report with only passing tests does not show module or test names`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(TestResult("passing fact", 1, emptyList(), emptyList(), false)),
+      )
+    )
+    resultsBuilder.setExamplesSection(
+      TestSectionResults(
+        TestResults.TestSectionName.EXAMPLES,
+        listOf(TestResult("passing example", 1, emptyList(), emptyList(), false)),
+      )
+    )
+    val testResults = resultsBuilder.build()
+
+    val writer = StringWriter()
+    val minimalReport = MinimalReporter(false)
+    minimalReport.report(testResults, writer)
+
+    assertThat(writer.toString()).isEmpty()
+  }
+
+  @Test
+  fun `report with failures shows module name and only failed tests`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(
+          TestResult("passing fact", 1, emptyList(), emptyList(), false),
+          TestResult(
+            "failing fact",
+            1,
+            listOf(TestResults.Failure("Fact Failure", "failed")),
+            emptyList(),
+            false,
+          ),
+        ),
+      )
+    )
+    resultsBuilder.setExamplesSection(
+      TestSectionResults(
+        TestResults.TestSectionName.EXAMPLES,
+        listOf(TestResult("passing example", 1, emptyList(), emptyList(), false)),
+      )
+    )
+    val testResults = resultsBuilder.build()
+
+    val writer = StringWriter()
+    val minimalReport = MinimalReporter(false)
+    minimalReport.report(testResults, writer)
+
+    val output = writer.toString()
+    assertThat(output).contains("module module1")
+    assertThat(output).contains("failing fact")
+    assertThat(output).doesNotContain("passing fact")
+    assertThat(output).doesNotContain("passing example")
+    assertThat(output).doesNotContain("examples")
+  }
+
+  @Test
+  fun `summarize includes stats even when all tests pass`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(TestResult("passing fact", 1, emptyList(), emptyList(), false)),
+      )
+    )
+    resultsBuilder.setExamplesSection(
+      TestSectionResults(TestResults.TestSectionName.EXAMPLES, emptyList())
+    )
+    val testResults = listOf(resultsBuilder.build())
+
+    val writer = StringWriter()
+    val minimalReport = MinimalReporter(false)
+    minimalReport.summarize(testResults, writer)
+
+    val output = writer.toString()
+    assertThat(output).contains("100.0% tests pass")
+    assertThat(output).contains("1 passed")
+  }
+
+  @Test
+  fun `summarize method should generate correct output for failures`() {
+    val resultsBuilder = TestResults.Builder("module1", "module1")
+    resultsBuilder.setFactsSection(
+      TestSectionResults(
+        TestResults.TestSectionName.FACTS,
+        listOf(
+          TestResult(
+            "example1",
+            321919,
+            listOf(TestResults.Failure("Fact Failure", "failed")),
+            emptyList(),
+            false,
+          )
+        ),
+      )
+    )
+    resultsBuilder.setExamplesSection(
+      TestSectionResults(
+        TestResults.TestSectionName.EXAMPLES,
+        listOf(
+          TestResult(
+            "example1",
+            432525,
+            listOf(TestResults.Failure("Output Mismatch", "does not match")),
+            emptyList(),
+            false,
+          )
+        ),
+      )
+    )
+    val testResults = listOf(resultsBuilder.build())
+
+    val writer = StringWriter()
+    val minimalReport = MinimalReporter(false)
+    minimalReport.summarize(testResults, writer)
+
+    val expectedOutput =
+      """
+      0.0% tests pass [2/2 failed], 99.9% asserts pass [2/754444 failed]
+      """
+        .trimIndent()
+
+    assertThat(writer.toString().trimIndent()).isEqualTo(expectedOutput)
+  }
+}

pkl-core/src/test/kotlin/org/pkl/core/stdlib/SimpleReportTest.kt

@@ -16,19 +16,18 @@
 package org.pkl.core.stdlib
 
 import java.io.StringWriter
-import java.util.*
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
 import org.pkl.core.TestResults
 import org.pkl.core.TestResults.TestResult
 import org.pkl.core.TestResults.TestSectionResults
-import org.pkl.core.stdlib.test.report.SimpleReport
+import org.pkl.core.stdlib.test.report.SpecReporter
 
 class SimpleReportTest {
 
   @Test
   fun `summarize method should generate correct output`() {
-    var resultsBuilder = TestResults.Builder("module1", "module1")
+    val resultsBuilder = TestResults.Builder("module1", "module1")
     resultsBuilder.setFactsSection(
       TestSectionResults(
         TestResults.TestSectionName.FACTS,
@@ -60,7 +59,7 @@ class SimpleReportTest {
     val testResults = listOf(resultsBuilder.build())
 
     val writer = StringWriter()
-    val simpleReport = SimpleReport(false)
+    val simpleReport = SpecReporter(false)
     simpleReport.summarize(testResults, writer)
 
     val expectedOutput =

pkl-gradle/src/main/java/org/pkl/gradle/PklPlugin.java

@@ -100,6 +100,7 @@ public class PklPlugin implements Plugin<Project> {
           spec.getOutputPath()
               .convention(project.getLayout().getBuildDirectory().dir("generated/pkl/packages"));
           spec.getOverwrite().convention(false);
+          spec.getReporter().convention("spec");
           var packageTask = createTask(project, ProjectPackageTask.class, spec);
           packageTask.configure(
               task -> {
@@ -108,6 +109,7 @@ public class PklPlugin implements Plugin<Project> {
                 task.getSkipPublishCheck().set(spec.getSkipPublishCheck());
                 task.getJunitReportsDir().set(spec.getJunitReportsDir());
                 task.getOverwrite().set(spec.getOverwrite());
+                task.getTestReporter().set(spec.getReporter());
               });
           project
               .getPluginManager()
@@ -278,12 +280,14 @@ public class PklPlugin implements Plugin<Project> {
           configureBaseSpec(project, spec);
 
           spec.getOverwrite().convention(false);
+          spec.getTestReporter().convention("spec");
 
           var testTask = createModulesTask(project, TestTask.class, spec);
           testTask.configure(
               task -> {
                 task.getJunitReportsDir().set(spec.getJunitReportsDir());
                 task.getOverwrite().set(spec.getOverwrite());
+                task.getTestReporter().set(spec.getTestReporter());
               });
 
           project

pkl-gradle/src/main/java/org/pkl/gradle/spec/ProjectPackageSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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.
@@ -29,4 +29,6 @@ public interface ProjectPackageSpec extends BasePklSpec {
   Property<Boolean> getOverwrite();
 
   Property<Boolean> getSkipPublishCheck();
+
+  Property<String> getReporter();
 }

pkl-gradle/src/main/java/org/pkl/gradle/spec/TestSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project 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.
@@ -22,4 +22,6 @@ public interface TestSpec extends ModulesSpec {
   DirectoryProperty getJunitReportsDir();
 
   Property<Boolean> getOverwrite();
+
+  Property<String> getTestReporter();
 }

pkl-gradle/src/main/java/org/pkl/gradle/task/ProjectPackageTask.java

@@ -34,6 +34,7 @@ import org.gradle.api.tasks.PathSensitivity;
 import org.gradle.api.tasks.UntrackedTask;
 import org.pkl.cli.CliProjectPackager;
 import org.pkl.commons.cli.CliTestOptions;
+import org.pkl.commons.cli.TestReporter;
 
 @UntrackedTask(because = "Output names are known only after execution")
 public abstract class ProjectPackageTask extends BasePklTask {
@@ -62,6 +63,10 @@ public abstract class ProjectPackageTask extends BasePklTask {
   @Optional
   public abstract Property<Boolean> getSkipPublishCheck();
 
+  @Input
+  @Optional
+  public abstract Property<String> getTestReporter();
+
   public ProjectPackageTask() {
     this.getJunitAggregateSuiteName().convention("pkl-tests");
   }
@@ -75,6 +80,18 @@ public abstract class ProjectPackageTask extends BasePklTask {
     if (projectDirectories.isEmpty()) {
       throw new InvalidUserDataException("No project directories specified.");
     }
+    TestReporter testReporter;
+    try {
+      testReporter = TestReporter.valueOf(getTestReporter().getOrElse("SPEC").toUpperCase());
+    } catch (IllegalArgumentException e) {
+      throw new InvalidUserDataException(
+          "Invalid reporter: '%s'. Valid reporter options: %s"
+              .formatted(
+                  getTestReporter().get(),
+                  TestReporter.getEntries().stream()
+                      .map(it -> it.name().toLowerCase())
+                      .collect(Collectors.joining(", "))));
+    }
 
     new CliProjectPackager(
             getCliBaseOptions(),
@@ -83,7 +100,8 @@ public abstract class ProjectPackageTask extends BasePklTask {
                 mapAndGetOrNull(getJunitReportsDir(), it -> it.getAsFile().toPath()),
                 getOverwrite().get(),
                 getJunitAggregateReports().getOrElse(false),
-                getJunitAggregateSuiteName().get()),
+                getJunitAggregateSuiteName().get(),
+                testReporter),
             getOutputPath().get().getAsFile().getAbsolutePath(),
             getSkipPublishCheck().getOrElse(false),
             new PrintWriter(System.out),

pkl-gradle/src/main/java/org/pkl/gradle/task/TestTask.java

@@ -18,6 +18,8 @@ package org.pkl.gradle.task;
 import static org.pkl.gradle.utils.PluginUtils.mapAndGetOrNull;
 
 import java.io.PrintWriter;
+import java.util.stream.Collectors;
+import org.gradle.api.InvalidUserDataException;
 import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.provider.Property;
 import org.gradle.api.tasks.CacheableTask;
@@ -26,6 +28,7 @@ import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.OutputDirectory;
 import org.pkl.cli.CliTestRunner;
 import org.pkl.commons.cli.CliTestOptions;
+import org.pkl.commons.cli.TestReporter;
 
 @CacheableTask
 public abstract class TestTask extends ModulesTask {
@@ -43,6 +46,10 @@ public abstract class TestTask extends ModulesTask {
   @Input
   public abstract Property<Boolean> getOverwrite();
 
+  @Input
+  @Optional
+  public abstract Property<String> getTestReporter();
+
   public TestTask() {
     this.getJunitAggregateSuiteName().convention("pkl-tests");
     this.getPowerAssertions().convention(true);
@@ -50,13 +57,26 @@ public abstract class TestTask extends ModulesTask {
 
   @Override
   protected void doRunTask() {
+    TestReporter testReporter;
+    try {
+      testReporter = TestReporter.valueOf(getTestReporter().getOrElse("SPEC").toUpperCase());
+    } catch (IllegalArgumentException e) {
+      throw new InvalidUserDataException(
+          "Invalid reporter: '%s'. Valid reporter options: %s"
+              .formatted(
+                  getTestReporter().get(),
+                  TestReporter.getEntries().stream()
+                      .map(it -> it.name().toLowerCase())
+                      .collect(Collectors.joining(", "))));
+    }
     new CliTestRunner(
             getCliBaseOptions(),
             new CliTestOptions(
                 mapAndGetOrNull(getJunitReportsDir(), it -> it.getAsFile().toPath()),
                 getOverwrite().get(),
                 getJunitAggregateReports().getOrElse(false),
-                getJunitAggregateSuiteName().get()),
+                getJunitAggregateSuiteName().get(),
+                testReporter),
             new PrintWriter(System.out),
             new PrintWriter(System.err))
         .run();