Adds testResource macro to core. Fix #1526.

buildSrc/src/main/java/io/micronaut/guides/core/TestResourceMacroSubstitution.java

@@ -0,0 +1,19 @@
+package io.micronaut.guides.core;
+
+import jakarta.inject.Singleton;
+
+import java.util.List;
+
+import static io.micronaut.guides.core.MacroUtils.addIncludesResources;
+
+@Singleton
+public class TestResourceMacroSubstitution implements MacroSubstitution{
+    @Override
+    public String substitute(String str, String slug, GuidesOption option) {
+        String resourceDir = "test";
+
+        List<String> lines = addIncludesResources(str,slug,option,resourceDir,"testResource");
+
+        return String.join("\n", lines);
+    }
+}

buildSrc/src/test/java/io/micronaut/guides/core/TestResourceMacroSubstitutionTest.java

@@ -0,0 +1,32 @@
+package io.micronaut.guides.core;
+
+import io.micronaut.starter.api.TestFramework;
+import io.micronaut.starter.options.BuildTool;
+import io.micronaut.starter.options.Language;
+import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
+import jakarta.inject.Inject;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@MicronautTest(startApplication = false)
+public class TestResourceMacroSubstitutionTest {
+
+    @Inject
+    TestResourceMacroSubstitution testResourceMacroSubstitution;
+
+    @Test
+    void testSubstitute() {
+        String str = "testResource:app/application-test.yml[tag=testcontainers]";
+        String resJava = testResourceMacroSubstitution.substitute(str, "micronaut-metrics-oci", new GuidesOption(BuildTool.GRADLE, Language.JAVA, TestFramework.JUNIT));
+        String expectedJava = """
+                [source,yaml]
+                .src/test/resources/application-test.yml
+                ----
+                include::{sourceDir}/micronaut-metrics-oci/micronaut-metrics-oci-gradle-java/src/test/resources/application-test.yml[tag=testcontainers]
+                
+                ----
+                """;
+        assertEquals(expectedJava, resJava);
+    }
+}