Additional tests for named container lookup

src/main/java/org/arquillian/testcontainers/TestcontainerRegistry.java

@@ -69,13 +69,35 @@ GenericContainer<?> lookupOrCreate(final Class<GenericContainer<?>> type, final
      */
     GenericContainer<?> lookup(final String name) {
         for (TestcontainerDescription containerDesc : this.containers) {
-            if (name.equals(containerDesc.name)) {
+            if (containerDesc.name.equals(name)) {
                 return containerDesc.instance;
             }
         }
         return null;
     }
 
+    /**
+     * Typed lookup by name. Throws {@link IllegalArgumentException} if a container with the given name is registered
+     * but its runtime type is not assignable to {@code type}.
+     *
+     * @param name the container name
+     * @param type the expected container type
+     *
+     * @return the container cast to {@code type}, or {@code null} if no container with the given name is registered
+     */
+    <T extends GenericContainer<?>> T lookup(final String name, final Class<T> type) {
+        final GenericContainer<?> container = lookup(name);
+        if (container == null) {
+            return null;
+        }
+        if (!type.isInstance(container)) {
+            throw new IllegalArgumentException(
+                    String.format("Container with name '%s' is of type %s, which is not assignable to %s",
+                            name, container.getClass().getName(), type.getName()));
+        }
+        return type.cast(container);
+    }
+
     /**
      * Lookup the container in the test container instances. If more than one container is found for the type or
      * qualifier, an {@link IllegalArgumentException} is thrown.

src/test/java/org/arquillian/testcontainers/NamedContainerTest.java

@@ -33,6 +33,9 @@ public static JavaArchive createDeployment() {
     @Testcontainer(name = "first")
     private SimpleTestContainer first;
 
+    @Testcontainer(name = "first")
+    private SimpleTestContainer firstAgain;
+
     @Testcontainer(name = "second")
     private SimpleTestContainer second;
 
@@ -59,4 +62,9 @@ public void checkAllDifferentInstances() {
         Assertions.assertNotSame(first, unnamed, "Expected named and unnamed containers to be different instances.");
         Assertions.assertNotSame(second, unnamed, "Expected named and unnamed containers to be different instances.");
     }
+
+    @Test
+    public void sameNameYieldsSameInstance() {
+        Assertions.assertSame(first, firstAgain, "Fields sharing a name must resolve to the same instance.");
+    }
 }

src/test/java/org/arquillian/testcontainers/TestcontainerRegistryTest.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright The Arquillian Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.arquillian.testcontainers;
+
+import java.lang.reflect.Field;
+import java.util.List;
+
+import org.arquillian.testcontainers.api.Testcontainer;
+import org.arquillian.testcontainers.common.SimpleTestContainer;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.testcontainers.containers.GenericContainer;
+
+/**
+ * Plain-JUnit unit tests for {@link TestcontainerRegistry} that exercise lookup semantics without
+ * starting any Docker containers. Annotation instances are obtained by reading the annotations off
+ * fixture fields on this class so the registry can be driven through {@code lookupOrCreate}
+ * outside an Arquillian context.
+ */
+public class TestcontainerRegistryTest {
+
+    @Testcontainer(name = "alpha")
+    private SimpleTestContainer alphaFixture;
+
+    @Test
+    public void sameNameViaLookupOrCreateReturnsSameInstance() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        GenericContainer<?> first = registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+        GenericContainer<?> second = registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        Assertions.assertSame(first, second);
+    }
+
+    @Test
+    public void lookupReturnsNullForUnknownName() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        Assertions.assertNull(registry.lookup("missing"));
+    }
+
+    @Test
+    public void emptyNameLookupDoesNotMatchNamedContainers() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        Assertions.assertNull(registry.lookup(""),
+                "Empty-string lookup should not return any registered container");
+    }
+
+    @Test
+    public void lookupTreatsNullNameAsAbsent() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        Assertions.assertNull(registry.lookup((String) null));
+    }
+
+    @Test
+    public void typedLookupReturnsTypedContainer() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        GenericContainer<?> alpha = registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        SimpleTestContainer typed = registry.lookup("alpha", SimpleTestContainer.class);
+        Assertions.assertSame(alpha, typed);
+        Assertions.assertNull(registry.lookup("missing", SimpleTestContainer.class));
+    }
+
+    @Test
+    public void typedLookupThrowsOnTypeMismatch() throws Exception {
+        TestcontainerRegistry registry = new TestcontainerRegistry();
+        registry.lookupOrCreate(simpleType(), annotation("alphaFixture"), List.of());
+
+        Assertions.assertThrows(IllegalArgumentException.class,
+                () -> registry.lookup("alpha", IncompatibleContainer.class));
+    }
+
+    /** Distinct {@link GenericContainer} subtype used to exercise the type-mismatch path on typed lookup. */
+    private static class IncompatibleContainer extends GenericContainer<IncompatibleContainer> {
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Class<GenericContainer<?>> simpleType() {
+        return (Class<GenericContainer<?>>) (Class<?>) SimpleTestContainer.class;
+    }
+
+    private Testcontainer annotation(final String fieldName) throws NoSuchFieldException {
+        final Field field = TestcontainerRegistryTest.class.getDeclaredField(fieldName);
+        return field.getAnnotation(Testcontainer.class);
+    }
+}