Fix README and add test for MP Config Provider

Author: kabir

integrations/microprofile-config/README.md

@@ -63,13 +63,18 @@ The `MicroProfileConfigProvider` implementation:
 ```
 MicroProfile Config Sources (application.properties, env vars, -D flags)
   ↓ (not found?)
-META-INF/a2a-defaults.properties (from server-common)
-  ↓ (not found?)
-META-INF/a2a-defaults.properties (from extras modules)
+DefaultValuesConfigProvider
+  → Scans classpath for ALL META-INF/a2a-defaults.properties files
+  → Merges all discovered properties together
+  → Throws exception if duplicate keys found
+  ↓ (property exists?)
+Return merged default value
   ↓ (not found?)
 IllegalArgumentException
 ```
 
+**Note**: All `META-INF/a2a-defaults.properties` files (from server-common, extras modules, etc.) are loaded and merged together by `DefaultValuesConfigProvider` at startup. This is not a sequential fallback chain, but a single merged set of defaults.
+
 ## Available Configuration Properties
 
 See the [main README](../../README.md#configuration-system) for a complete list of configuration properties.

integrations/microprofile-config/pom.xml

@@ -38,5 +38,22 @@
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-api</artifactId>
         </dependency>
+
+        <!-- Test dependencies -->
+        <dependency>
+            <groupId>io.quarkus</groupId>
+            <artifactId>quarkus-arc</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.quarkus</groupId>
+            <artifactId>quarkus-junit5</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

integrations/microprofile-config/src/test/java/io/a2a/integrations/microprofile/MicroProfileConfigProviderTest.java

@@ -0,0 +1,102 @@
+package io.a2a.integrations.microprofile;
+
+import io.a2a.server.config.A2AConfigProvider;
+import io.quarkus.test.junit.QuarkusTest;
+import jakarta.inject.Inject;
+import org.junit.jupiter.api.Test;
+
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * CDI-based test to verify that MicroProfileConfigProvider is properly selected
+ * and works correctly with MicroProfile Config and fallback to defaults.
+ */
+@QuarkusTest
+public class MicroProfileConfigProviderTest {
+
+    @Inject
+    A2AConfigProvider configProvider;
+
+    @Test
+    public void testIsMicroProfileConfigProvider() {
+        // Verify that when microprofile-config module is on classpath,
+        // the injected A2AConfigProvider is the MicroProfile implementation
+        assertInstanceOf(MicroProfileConfigProvider.class, configProvider,
+                "A2AConfigProvider should be MicroProfileConfigProvider when module is present");
+    }
+
+    @Test
+    public void testGetValueFromMicroProfileConfig() {
+        // Test that values from application.properties override defaults
+        // The test application.properties sets a2a.executor.core-pool-size=15
+        String value = configProvider.getValue("a2a.executor.core-pool-size");
+        assertEquals("15", value, "Should get value from MicroProfile Config (application.properties)");
+    }
+
+    @Test
+    public void testGetValueFallbackToDefaults() {
+        // Test that values not in application.properties fall back to META-INF/a2a-defaults.properties
+        // a2a.executor.max-pool-size is not in test application.properties, so should use default
+        String value = configProvider.getValue("a2a.executor.max-pool-size");
+        assertEquals("50", value, "Should fall back to default value from META-INF/a2a-defaults.properties");
+    }
+
+    @Test
+    public void testGetValueAnotherDefault() {
+        // Test another default property to ensure fallback works
+        String value = configProvider.getValue("a2a.executor.keep-alive-seconds");
+        assertEquals("60", value, "Should fall back to default value");
+    }
+
+    @Test
+    public void testGetOptionalValueFromMicroProfileConfig() {
+        // Test optional value that exists in application.properties
+        Optional<String> value = configProvider.getOptionalValue("a2a.executor.core-pool-size");
+        assertTrue(value.isPresent(), "Optional value should be present");
+        assertEquals("15", value.get(), "Should get overridden value from MicroProfile Config");
+    }
+
+    @Test
+    public void testGetOptionalValueFallbackToDefaults() {
+        // Test optional value that falls back to defaults
+        Optional<String> value = configProvider.getOptionalValue("a2a.executor.max-pool-size");
+        assertTrue(value.isPresent(), "Optional value should be present from defaults");
+        assertEquals("50", value.get(), "Should get default value");
+    }
+
+    @Test
+    public void testGetOptionalValueNotFound() {
+        // Test optional value that doesn't exist anywhere
+        Optional<String> value = configProvider.getOptionalValue("non.existent.property");
+        assertFalse(value.isPresent(), "Optional value should be empty for non-existent property");
+    }
+
+    @Test
+    public void testGetValueThrowsForNonExistent() {
+        // Test that required getValue() throws for non-existent property
+        assertThrows(IllegalArgumentException.class,
+                () -> configProvider.getValue("non.existent.property"),
+                "Should throw IllegalArgumentException for non-existent required property");
+    }
+
+    @Test
+    public void testSystemPropertyOverride() {
+        // System properties should have higher priority than application.properties
+        // Set a system property and verify it's used
+        String originalValue = System.getProperty("a2a.test.system.property");
+        try {
+            System.setProperty("a2a.test.system.property", "from-system-property");
+            String value = configProvider.getValue("a2a.test.system.property");
+            assertEquals("from-system-property", value,
+                    "System property should override application.properties");
+        } finally {
+            if (originalValue != null) {
+                System.setProperty("a2a.test.system.property", originalValue);
+            } else {
+                System.clearProperty("a2a.test.system.property");
+            }
+        }
+    }
+}

integrations/microprofile-config/src/test/resources/application.properties

@@ -0,0 +1,11 @@
+# Test configuration for MicroProfileConfigProviderTest
+# This overrides the default value to verify MicroProfile Config integration works
+
+# Override default value (default is 5)
+a2a.executor.core-pool-size=15
+
+# Note: a2a.executor.max-pool-size is NOT set here to test fallback to defaults
+# Default value should be 50 from META-INF/a2a-defaults.properties
+
+# Exclude beans that aren't needed for config testing
+quarkus.arc.exclude-types=io.a2a.server.requesthandlers.*,io.a2a.server.agentexecution.*,io.a2a.server.tasks.*,io.a2a.server.events.*,io.a2a.server.util.*