Merge branch 'test'

20 files changed, 410 insertions, 33 deletions

diff --git a/pom.xml b/pom.xml
index 3ae6035..90d166e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -56,6 +56,12 @@
 
             <dependency>
                 <groupId>com.tavianator.sangria</groupId>
+                <artifactId>sangria-test</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+
+            <dependency>
+                <groupId>com.tavianator.sangria</groupId>
                 <artifactId>sangria-contextual</artifactId>
                 <version>${project.version}</version>
             </dependency>
@@ -87,13 +93,13 @@
             <dependency>
                 <groupId>com.google.inject</groupId>
                 <artifactId>guice</artifactId>
-                <version>4.0-beta4</version>
+                <version>4.0-beta5</version>
             </dependency>
 
             <dependency>
                 <groupId>com.google.inject.extensions</groupId>
                 <artifactId>guice-multibindings</artifactId>
-                <version>4.0-beta4</version>
+                <version>4.0-beta5</version>
             </dependency>
 
             <dependency>
@@ -290,6 +296,7 @@
 
     <modules>
         <module>sangria-core</module>
+        <module>sangria-test</module>
         <module>sangria-contextual</module>
         <module>sangria-slf4j</module>
         <module>sangria-log4j</module>
diff --git a/sangria-contextual/pom.xml b/sangria-contextual/pom.xml
index c939076..702616f 100644
--- a/sangria-contextual/pom.xml
+++ b/sangria-contextual/pom.xml
@@ -38,6 +38,12 @@
         </dependency>
 
         <dependency>
+            <groupId>com.tavianator.sangria</groupId>
+            <artifactId>sangria-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
diff --git a/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java b/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
index 6d5e502..fdc1ad0 100644
--- a/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
+++ b/sangria-contextual/src/main/java/com/tavianator/sangria/contextual/ContextSensitiveBinder.java
@@ -40,6 +40,7 @@ import com.google.inject.spi.ProviderWithExtensionVisitor;
 import com.google.inject.spi.ProvisionListener;
 
 import com.tavianator.sangria.core.DelayedError;
+import com.tavianator.sangria.core.UniqueAnnotations;
 
 /**
  * A binder for {@link ContextSensitiveProvider}s.
@@ -139,10 +140,17 @@ public class ContextSensitiveBinder {
         public void toContextSensitiveProvider(Key<? extends ContextSensitiveProvider<? extends T>> key) {
             error.cancel();
 
-            binder.bind(bindingKey).toProvider(new ProviderKeyAdapter<>(key));
+            binder.bind(bindingKey).toProvider(new ProviderKeyAdapter<>(key, makeLinkedKey(key)));
             binder.bindListener(new BindingMatcher(bindingKey), new Trigger(bindingKey));
         }
 
+        private <U> Key<U> makeLinkedKey(Key<U> key) {
+            Key<U> linkedKey = Key.get(key.getTypeLiteral(), UniqueAnnotations.create());
+            binder.bind(linkedKey)
+                    .to(key);
+            return linkedKey;
+        }
+
         @Override
         public void toContextSensitiveProvider(ContextSensitiveProvider<? extends T> provider) {
             error.cancel();
@@ -190,15 +198,19 @@ public class ContextSensitiveBinder {
 
     private static class ProviderKeyAdapter<T> extends ProviderAdapter<T> implements ContextSensitiveProviderKeyBinding<T> {
         private final Key<? extends ContextSensitiveProvider<? extends T>> providerKey;
+        private final Key<? extends ContextSensitiveProvider<? extends T>> linkedKey;
         private Provider<? extends ContextSensitiveProvider<? extends T>> provider;
 
-        ProviderKeyAdapter(Key<? extends ContextSensitiveProvider<? extends T>> providerKey) {
+        ProviderKeyAdapter(
+                Key<? extends ContextSensitiveProvider<? extends T>> providerKey,
+                Key<? extends ContextSensitiveProvider<? extends T>> linkedKey) {
             this.providerKey = providerKey;
+            this.linkedKey = linkedKey;
         }
 
         @Inject
         void inject(Injector injector) {
-            provider = injector.getProvider(providerKey);
+            provider = injector.getProvider(linkedKey);
         }
 
         @Override
diff --git a/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java b/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
index 1e2ab49..68250cb 100644
--- a/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
+++ b/sangria-contextual/src/test/java/com/tavianator/sangria/contextual/ContextSensitiveBinderTest.java
@@ -28,6 +28,7 @@ import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.google.inject.Key;
 import com.google.inject.MembersInjector;
+import com.google.inject.Module;
 import com.google.inject.Provider;
 import com.google.inject.ProvisionException;
 import com.google.inject.TypeLiteral;
@@ -40,6 +41,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -54,6 +56,10 @@ public class ContextSensitiveBinderTest {
     public @Rule ExpectedException thrown = ExpectedException.none();
 
     private static class SelfProvider implements ContextSensitiveProvider<String> {
+        @Inject
+        SelfProvider() {
+        }
+
         // For testing getInjectionPoints() in the SPI below
         @SuppressWarnings("unused")
         @Inject Injector injector;
@@ -191,6 +197,21 @@ public class ContextSensitiveBinderTest {
         assertThat(hasSelf.selfProvider.get(), equalTo("<unknown>"));
     }
 
+    @Test
+    public void testBestPractices() {
+        Module module = new AbstractModule() {
+            @Override
+            protected void configure() {
+                ContextSensitiveBinder.create(binder())
+                        .bind(String.class)
+                        .annotatedWith(Names.named("self"))
+                        .toContextSensitiveProvider(SelfProvider.class);
+            }
+        };
+        assertThat(module, is(atomic()));
+        assertThat(module, followsBestPractices());
+    }
+
     private static class RequiredContextProvider implements ContextSensitiveProvider<String> {
         @Override
         public String getInContext(InjectionPoint injectionPoint) {
diff --git a/sangria-lazy/pom.xml b/sangria-lazy/pom.xml
index 4840af3..e2c806e 100644
--- a/sangria-lazy/pom.xml
+++ b/sangria-lazy/pom.xml
@@ -38,6 +38,12 @@
         </dependency>
 
         <dependency>
+            <groupId>com.tavianator.sangria</groupId>
+            <artifactId>sangria-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
diff --git a/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/SangriaLazyModule.java b/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/SangriaLazyModule.java
index ff4a02a..57cf763 100644
--- a/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/SangriaLazyModule.java
+++ b/sangria-lazy/src/main/java/com/tavianator/sangria/lazy/SangriaLazyModule.java
@@ -31,14 +31,4 @@ public class SangriaLazyModule extends AbstractModule {
     protected void configure() {
         bindScope(LazySingleton.class, LazyScopes.LAZY_SINGLETON);
     }
-
-    @Override
-    public boolean equals(Object o) {
-        return o instanceof SangriaLazyModule;
-    }
-
-    @Override
-    public int hashCode() {
-        return SangriaLazyModule.class.hashCode();
-    }
 }
diff --git a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazySingletonTest.java b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazySingletonTest.java
index 69fabce..2895c7d 100644
--- a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazySingletonTest.java
+++ b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazySingletonTest.java
@@ -20,12 +20,14 @@ package com.tavianator.sangria.lazy;
 import javax.inject.Inject;
 import javax.inject.Provider;
 
+import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.google.inject.Module;
 import com.google.inject.Stage;
 import org.junit.Test;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -62,11 +64,6 @@ public class LazySingletonTest {
         test(Stage.PRODUCTION, new SangriaLazyModule());
     }
 
-    @Test
-    public void testDuplicateModule() {
-        test(Stage.PRODUCTION, new SangriaLazyModule(), new SangriaLazyModule());
-    }
-
     private void test(Stage stage, Module... modules) {
         int before = Scoped.INSTANCES.get();
 
@@ -80,4 +77,18 @@ public class LazySingletonTest {
         assertThat(provider.get(), sameInstance(instance));
         assertThat(Scoped.INSTANCES.get(), equalTo(before + 1));
     }
+
+    @Test
+    public void testBestPractices() {
+        Module module = new AbstractModule() {
+            @Override
+            protected void configure() {
+                install(new SangriaLazyModule());
+                bind(Scoped.class);
+            }
+        };
+
+        assertThat(module, is(atomic()));
+        assertThat(module, followsBestPractices());
+    }
 }
diff --git a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
index ff63c03..8bea02d 100644
--- a/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
+++ b/sangria-lazy/src/test/java/com/tavianator/sangria/lazy/LazyTest.java
@@ -35,6 +35,7 @@ import com.google.inject.spi.Element;
 import com.google.inject.spi.Elements;
 import org.junit.Test;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -69,7 +70,12 @@ public class LazyTest {
     }
 
     private static class HasConcrete {
-        @Inject Lazy<Concrete> lazy;
+        final Lazy<Concrete> lazy;
+
+        @Inject
+        HasConcrete(Lazy<Concrete> lazy) {
+            this.lazy = lazy;
+        }
     }
 
     private static class HasQualifiedAbstract {
@@ -88,6 +94,8 @@ public class LazyTest {
             protected void configure() {
                 binder().requireExplicitBindings();
 
+                bind(HasConcrete.class);
+
                 bind(Concrete.class);
                 LazyBinder.create(binder())
                         .bind(Concrete.class);
@@ -95,11 +103,26 @@ public class LazyTest {
         }));
     }
 
+    @Test
+    public void testBestPractices() {
+        Module module = new AbstractModule() {
+            @Override
+            protected void configure() {
+                bind(HasConcrete.class);
+
+                bind(Concrete.class);
+                LazyBinder.create(binder())
+                        .bind(Concrete.class);
+            }
+        };
+        assertThat(module, is(atomic()));
+        assertThat(module, followsBestPractices());
+    }
+
     private void testHasConcrete(Injector injector) {
         int before = Concrete.INSTANCES.get();
 
-        HasConcrete hasConcrete = new HasConcrete();
-        injector.injectMembers(hasConcrete);
+        HasConcrete hasConcrete = injector.getInstance(HasConcrete.class);
         assertThat(Concrete.INSTANCES.get(), equalTo(before));
 
         Concrete instance = hasConcrete.lazy.get();
@@ -109,8 +132,7 @@ public class LazyTest {
         assertThat(instance2, sameInstance(instance));
         assertThat(Concrete.INSTANCES.get(), equalTo(before + 1));
 
-        HasConcrete hasConcrete2 = new HasConcrete();
-        injector.injectMembers(hasConcrete2);
+        HasConcrete hasConcrete2 = injector.getInstance(HasConcrete.class);
         assertThat(Concrete.INSTANCES.get(), equalTo(before + 1));
 
         Concrete instance3 = hasConcrete2.lazy.get();
@@ -150,8 +172,7 @@ public class LazyTest {
     private void testQualifiedAbstract(Injector injector) {
         int before = Concrete.INSTANCES.get();
 
-        HasQualifiedAbstract hasQualifiedAbstract = new HasQualifiedAbstract();
-        injector.injectMembers(hasQualifiedAbstract);
+        HasQualifiedAbstract hasQualifiedAbstract = injector.getInstance(HasQualifiedAbstract.class);
         assertThat(Concrete.INSTANCES.get(), equalTo(before));
 
         Abstract instance = hasQualifiedAbstract.lazy.get();
@@ -161,8 +182,7 @@ public class LazyTest {
         assertThat(instance2, sameInstance(instance2));
         assertThat(Concrete.INSTANCES.get(), equalTo(before + 1));
 
-        HasQualifiedAbstract hasQualifiedAbstract2 = new HasQualifiedAbstract();
-        injector.injectMembers(hasQualifiedAbstract2);
+        HasQualifiedAbstract hasQualifiedAbstract2 = injector.getInstance(HasQualifiedAbstract.class);
         assertThat(Concrete.INSTANCES.get(), equalTo(before + 1));
 
         Abstract instance3 = hasQualifiedAbstract2.lazy.get();
diff --git a/sangria-log4j/pom.xml b/sangria-log4j/pom.xml
index 224081d..06e892a 100644
--- a/sangria-log4j/pom.xml
+++ b/sangria-log4j/pom.xml
@@ -39,6 +39,12 @@
         </dependency>
 
         <dependency>
+            <groupId>com.tavianator.sangria</groupId>
+            <artifactId>sangria-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
diff --git a/sangria-log4j/src/main/java/com/tavianator/sangria/log4j/Log4jLoggerProvider.java b/sangria-log4j/src/main/java/com/tavianator/sangria/log4j/Log4jLoggerProvider.java
index dae2323..34262d7 100644
--- a/sangria-log4j/src/main/java/com/tavianator/sangria/log4j/Log4jLoggerProvider.java
+++ b/sangria-log4j/src/main/java/com/tavianator/sangria/log4j/Log4jLoggerProvider.java
@@ -19,6 +19,7 @@ package com.tavianator.sangria.log4j;
 
 import javax.inject.Singleton;
 
+import com.google.inject.Inject;
 import com.google.inject.spi.InjectionPoint;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -34,6 +35,10 @@ import com.tavianator.sangria.contextual.ContextSensitiveProvider;
  */
 @Singleton
 class Log4jLoggerProvider implements ContextSensitiveProvider<Logger> {
+    @Inject
+    Log4jLoggerProvider() {
+    }
+
     @Override
     public Logger getInContext(InjectionPoint injectionPoint) {
         return LogManager.getLogger(injectionPoint.getDeclaringType().getRawType());
diff --git a/sangria-log4j/src/test/java/com/tavianator/sangria/log4j/SangriaLog4jModuleTest.java b/sangria-log4j/src/test/java/com/tavianator/sangria/log4j/SangriaLog4jModuleTest.java
index d91cf90..a3ecd66 100644
--- a/sangria-log4j/src/test/java/com/tavianator/sangria/log4j/SangriaLog4jModuleTest.java
+++ b/sangria-log4j/src/test/java/com/tavianator/sangria/log4j/SangriaLog4jModuleTest.java
@@ -29,6 +29,7 @@ import org.apache.logging.log4j.Logger;
 import org.junit.Before;
 import org.junit.Test;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -74,7 +75,8 @@ public class SangriaLog4jModuleTest {
     }
 
     @Test
-    public void testDeDuplication() {
-        Guice.createInjector(new SangriaLog4jModule(), new SangriaLog4jModule());
+    public void testBestPractices() {
+        assertThat(new SangriaLog4jModule(), is(atomic()));
+        assertThat(new SangriaLog4jModule(), followsBestPractices());
     }
 }
diff --git a/sangria-slf4j/pom.xml b/sangria-slf4j/pom.xml
index c274a47..53cbfb7 100644
--- a/sangria-slf4j/pom.xml
+++ b/sangria-slf4j/pom.xml
@@ -39,6 +39,12 @@
         </dependency>
 
         <dependency>
+            <groupId>com.tavianator.sangria</groupId>
+            <artifactId>sangria-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+        <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <scope>test</scope>
diff --git a/sangria-slf4j/src/main/java/com/tavianator/sangria/slf4j/Slf4jLoggerProvider.java b/sangria-slf4j/src/main/java/com/tavianator/sangria/slf4j/Slf4jLoggerProvider.java
index 916f2b9..bcb7e8b 100644
--- a/sangria-slf4j/src/main/java/com/tavianator/sangria/slf4j/Slf4jLoggerProvider.java
+++ b/sangria-slf4j/src/main/java/com/tavianator/sangria/slf4j/Slf4jLoggerProvider.java
@@ -19,6 +19,7 @@ package com.tavianator.sangria.slf4j;
 
 import javax.inject.Singleton;
 
+import com.google.inject.Inject;
 import com.google.inject.spi.InjectionPoint;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -34,6 +35,10 @@ import com.tavianator.sangria.contextual.ContextSensitiveProvider;
  */
 @Singleton
 class Slf4jLoggerProvider implements ContextSensitiveProvider<Logger> {
+    @Inject
+    Slf4jLoggerProvider() {
+    }
+
     @Override
     public Logger getInContext(InjectionPoint injectionPoint) {
         return LoggerFactory.getLogger(injectionPoint.getDeclaringType().getRawType());
diff --git a/sangria-slf4j/src/test/java/com/tavianator/sangria/slf4j/SangriaSlf4jModuleTest.java b/sangria-slf4j/src/test/java/com/tavianator/sangria/slf4j/SangriaSlf4jModuleTest.java
index d142bde..aaf72b2 100644
--- a/sangria-slf4j/src/test/java/com/tavianator/sangria/slf4j/SangriaSlf4jModuleTest.java
+++ b/sangria-slf4j/src/test/java/com/tavianator/sangria/slf4j/SangriaSlf4jModuleTest.java
@@ -28,6 +28,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.slf4j.Logger;
 
+import static com.tavianator.sangria.test.SangriaMatchers.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -75,7 +76,8 @@ public class SangriaSlf4jModuleTest {
     }
 
     @Test
-    public void testDeDuplication() {
-        Guice.createInjector(new SangriaSlf4jModule(), new SangriaSlf4jModule());
+    public void testBestPractices() {
+        assertThat(new SangriaSlf4jModule(), is(atomic()));
+        assertThat(new SangriaSlf4jModule(), followsBestPractices());
     }
 }
diff --git a/sangria-test/pom.xml b/sangria-test/pom.xml
new file mode 100644
index 0000000..cdb835d
--- /dev/null
+++ b/sangria-test/pom.xml
@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.tavianator.sangria</groupId>
+        <artifactId>sangria</artifactId>
+        <version>1.2-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>sangria-test</artifactId>
+    <packaging>jar</packaging>
+    <name>Sangria Test</name>
+    <description>Utilities for testing with Guice</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.inject</groupId>
+            <artifactId>guice</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>jsr305</artifactId>
+            <optional>true</optional>
+        </dependency>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest-integration</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>
diff --git a/sangria-test/src/main/java/com/tavianator/sangria/test/AtomicMatcher.java b/sangria-test/src/main/java/com/tavianator/sangria/test/AtomicMatcher.java
new file mode 100644
index 0000000..03c897e
--- /dev/null
+++ b/sangria-test/src/main/java/com/tavianator/sangria/test/AtomicMatcher.java
@@ -0,0 +1,38 @@
+package com.tavianator.sangria.test;
+
+import com.google.inject.CreationException;
+import com.google.inject.Guice;
+import com.google.inject.Module;
+import com.google.inject.spi.Elements;
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+/**
+ * Matcher that checks whether a {@link Module} can be installed multiple times.
+ *
+ * @author Tavian Barnes (tavianator@tavianator.com)
+ * @version 1.2
+ * @since 1.2
+ */
+final class AtomicMatcher extends TypeSafeDiagnosingMatcher<Module> {
+    @Override
+    protected boolean matchesSafely(Module item, Description mismatchDescription) {
+        // Pass through the SPI to make sure the Module is atomic regardless of its equals() implementation
+        // This ensures atomicity even through Modules.override(), for example
+        Module copy1 = Elements.getModule(Elements.getElements(item));
+        Module copy2 = Elements.getModule(Elements.getElements(item));
+
+        try {
+            Guice.createInjector(copy1, copy2);
+            return true;
+        } catch (CreationException e) {
+            mismatchDescription.appendValue(e);
+            return false;
+        }
+    }
+
+    @Override
+    public void describeTo(Description description) {
+        description.appendText("an atomic Module");
+    }
+}
diff --git a/sangria-test/src/main/java/com/tavianator/sangria/test/BestPracticesMatcher.java b/sangria-test/src/main/java/com/tavianator/sangria/test/BestPracticesMatcher.java
new file mode 100644
index 0000000..36eea97
--- /dev/null
+++ b/sangria-test/src/main/java/com/tavianator/sangria/test/BestPracticesMatcher.java
@@ -0,0 +1,42 @@
+package com.tavianator.sangria.test;
+
+import com.google.inject.AbstractModule;
+import com.google.inject.CreationException;
+import com.google.inject.Guice;
+import com.google.inject.Module;
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+/**
+ * Matcher that checks whether a {@link Module} follows Guice best practices.
+ *
+ * @author Tavian Barnes (tavianator@tavianator.com)
+ * @version 1.2
+ * @since 1.2
+ */
+final class BestPracticesMatcher extends TypeSafeDiagnosingMatcher<Module> {
+    private static final class EnforcerModule extends AbstractModule {
+        @Override
+        protected void configure() {
+            binder().requireAtInjectOnConstructors();
+            binder().requireExactBindingAnnotations();
+            binder().requireExplicitBindings();
+        }
+    }
+
+    @Override
+    protected boolean matchesSafely(Module item, Description mismatchDescription) {
+        try {
+            Guice.createInjector(item, new EnforcerModule());
+            return true;
+        } catch (CreationException e) {
+            mismatchDescription.appendValue(e);
+            return false;
+        }
+    }
+
+    @Override
+    public void describeTo(Description description) {
+        description.appendText("a Module following Guice best practices");
+    }
+}
diff --git a/sangria-test/src/main/java/com/tavianator/sangria/test/SangriaMatchers.java b/sangria-test/src/main/java/com/tavianator/sangria/test/SangriaMatchers.java
new file mode 100644
index 0000000..da8dd74
--- /dev/null
+++ b/sangria-test/src/main/java/com/tavianator/sangria/test/SangriaMatchers.java
@@ -0,0 +1,31 @@
+package com.tavianator.sangria.test;
+
+import com.google.inject.Module;
+import org.hamcrest.Matcher;
+
+/**
+ * Guice-related Hamcrest matchers.
+ *
+ * @author Tavian Barnes (tavianator@tavianator.com)
+ * @version 1.2
+ * @since 1.2
+ */
+public final class SangriaMatchers {
+    private SangriaMatchers() {
+        // Not for instantiating
+    }
+
+    /**
+     * @return A {@link Matcher} that checks whether a {@link Module}'s bindings can be de-duplicated successfully.
+     */
+    public static Matcher<Module> atomic() {
+        return new AtomicMatcher();
+    }
+
+    /**
+     * @return A {@link Matcher} that checks whether a {@link Module} follows Guice best practices.
+     */
+    public static Matcher<Module> followsBestPractices() {
+        return new BestPracticesMatcher();
+    }
+}
diff --git a/sangria-test/src/main/java/com/tavianator/sangria/test/package-info.java b/sangria-test/src/main/java/com/tavianator/sangria/test/package-info.java
new file mode 100644
index 0000000..0375640
--- /dev/null
+++ b/sangria-test/src/main/java/com/tavianator/sangria/test/package-info.java
@@ -0,0 +1,25 @@
+/****************************************************************************
+ * Sangria                                                                  *
+ * Copyright (C) 2014 Tavian Barnes <tavianator@tavianator.com>             *
+ *                                                                          *
+ * 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                                  *
+ *                                                                          *
+ * http://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.                                           *
+ ****************************************************************************/
+
+/**
+ * {@code sangria-test}: Utilities for testing with Guice.
+ *
+ * @author Tavian Barnes (tavianator@tavianator.com)
+ * @version 1.2
+ * @since 1.2
+ */
+package com.tavianator.sangria.test;
diff --git a/sangria-test/src/test/java/com/tavianator/sangria/test/SangriaMatchersTest.java b/sangria-test/src/test/java/com/tavianator/sangria/test/SangriaMatchersTest.java
new file mode 100644
index 0000000..06fb45e
--- /dev/null
+++ b/sangria-test/src/test/java/com/tavianator/sangria/test/SangriaMatchersTest.java
@@ -0,0 +1,91 @@
+package com.tavianator.sangria.test;
+
+import javax.inject.Inject;
+import javax.inject.Named;
+
+import com.google.inject.AbstractModule;
+import com.google.inject.Provides;
+import org.junit.Test;
+
+import static com.tavianator.sangria.test.SangriaMatchers.*;
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+/**
+ * Tests for {@link SangriaMatchers}.
+ *
+ * @author Tavian Barnes (tavianator@tavianator.com)
+ * @version 1.2
+ * @since 1.2
+ */
+public class SangriaMatchersTest {
+    private static class AtomicModule extends AbstractModule {
+        private static final Object INSTANCE = new Object();
+
+        @Override
+        protected void configure() {
+            bind(Object.class)
+                    .toInstance(INSTANCE);
+        }
+    }
+
+    private static class NonAtomicModule extends AbstractModule {
+        @Override
+        protected void configure() {
+            bind(Object.class)
+                    .toInstance(new Object());
+        }
+    }
+
+    @Test
+    public void testAtomic() {
+        assertThat(new AtomicModule(), is(atomic()));
+        assertThat(new NonAtomicModule(), is(not(atomic())));
+    }
+
+    private static class NoAtInjectModule extends AbstractModule {
+        @Override
+        protected void configure() {
+            bind(String.class);
+        }
+    }
+
+    private static class InexactBindingAnnotationModule extends AbstractModule {
+        @Override
+        protected void configure() {
+            bind(String.class)
+                    .annotatedWith(Named.class)
+                    .toInstance("test");
+        }
+
+        @Provides
+        String getString(@Named("test") String test) {
+            return test;
+        }
+    }
+
+    private static class Injectable {
+        @Inject
+        Injectable() {
+        }
+    }
+
+    private static class JustInTimeModule extends AbstractModule {
+        @Override
+        protected void configure() {
+        }
+
+        @Provides
+        String getString(Injectable injectable) {
+            return "test";
+        }
+    }
+
+    @Test
+    public void testFollowsBestPractices() {
+        assertThat(new AtomicModule(), followsBestPractices());
+        assertThat(new NoAtInjectModule(), not(followsBestPractices()));
+        assertThat(new InexactBindingAnnotationModule(), not(followsBestPractices()));
+        assertThat(new JustInTimeModule(), not(followsBestPractices()));
+    }
+}