Added test for dynamic collection names

Closes #2764

Author: marcingrzejszczak

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/mapping/BasicMongoPersistentEntityUnitTests.java

@@ -34,12 +34,14 @@
 
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.annotation.AliasFor;
+import org.springframework.core.env.Environment;
 import org.springframework.core.env.StandardEnvironment;
 import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.data.spel.ExtensionAwareEvaluationContextProvider;
 import org.springframework.data.spel.spi.EvaluationContextExtension;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.mock.env.MockEnvironment;
 
 /**
  * Unit tests for {@link BasicMongoPersistentEntity}.
@@ -87,6 +89,19 @@ void collectionAllowsReferencingSpringBean() {
 		assertThat(entity.getCollection()).isEqualTo("otherReference");
 	}
 
+	@Test // GH-2764
+	void collectionAllowsReferencingProperties() {
+
+		MockEnvironment environment = new MockEnvironment();
+		environment.setProperty("collectionName", "reference");
+
+		BasicMongoPersistentEntity<DynamicallyMappedUsingPropertyPlaceholder> entity = new BasicMongoPersistentEntity<>(
+				TypeInformation.of(DynamicallyMappedUsingPropertyPlaceholder.class));
+		entity.setEnvironment(environment);
+
+		assertThat(entity.getCollection()).isEqualTo("reference_cat");
+	}
+
 	@Test // DATAMONGO-937
 	void shouldDetectLanguageCorrectly() {
 
@@ -325,6 +340,9 @@ class Company {}
 	@Document("#{@myBean.collectionName}")
 	class DynamicallyMapped {}
 
+	@Document("${collectionName}_cat")
+	class DynamicallyMappedUsingPropertyPlaceholder {}
+
 	class CollectionProvider {
 		String collectionName;