Add javadocs to various places.

community/kernel-api/src/main/java/org/neo4j/internal/kernel/api/Write.java

@@ -26,27 +26,93 @@
  */
 public interface Write
 {
+    /**
+     * Create a node.
+     * @return The internal id of the created node
+     */
     long nodeCreate();
 
+    /**
+     * Delete a node.
+     * @param node the internal id of the node to delete
+     */
     void nodeDelete( long node );
 
+    /**
+     * Create a relationship between two nodes.
+     * @param sourceNode the source internal node id
+     * @param relationshipLabel the label of the relationship to create
+     * @param targetNode the target internal node id
+     * @return the internal id of the created relationship
+     */
     long relationshipCreate( long sourceNode, int relationshipLabel, long targetNode );
 
+    /**
+     * Delete a relationship
+     * @param relationship the internal id of the relationship to delete
+     */
     void relationshipDelete( long relationship );
 
+    /**
+     * Add a label to a node
+     * @param node the internal node id
+     * @param nodeLabel the internal id of the label to add
+     */
     void nodeAddLabel( long node, int nodeLabel );
 
+    /**
+     * Remove a label from a node
+     * @param node the internal node id
+     * @param nodeLabel the internal id of the label to remove
+     */
     void nodeRemoveLabel( long node, int nodeLabel );
 
+    /**
+     * Set a property on a node
+     * @param node the internal node id
+     * @param propertyKey the property key id
+     * @param value the value to set
+     * @return The replaced value, or Values.NO_VALUE if the node did not have the property before
+     */
     Value nodeSetProperty( long node, int propertyKey, Value value );
 
+    /**
+     * Remove a property from a node
+     * @param node the internal node id
+     * @param propertyKey the property key id
+     * @return The removed value, or Values.NO_VALUE if the node did not have the property before
+     */
     Value nodeRemoveProperty( long node, int propertyKey );
 
+    /**
+     * Set a property on a relationship
+     * @param relationship the internal relationship id
+     * @param propertyKey the property key id
+     * @param value the value to set
+     * @return The replaced value, or Values.NO_VALUE if the relationship did not have the property before
+     */
     Value relationshipSetProperty( long relationship, int propertyKey, Value value );
 
+    /**
+     * Remove a property from a relationship
+     * @param node the internal relationship id
+     * @param propertyKey the property key id
+     * @return The removed value, or Values.NO_VALUE if the relationship did not have the property before
+     */
     Value relationshipRemoveProperty( long node, int propertyKey );
 
+    /**
+     * Set a property on the graph
+     * @param propertyKey the property key id
+     * @param value the value to set
+     * @return The replaced value, or Values.NO_VALUE if the graph did not have the property before
+     */
     Value graphSetProperty( int propertyKey, Value value );
 
+    /**
+     * Remove a property from the graph
+     * @param propertyKey the property key id
+     * @return The removed value, or Values.NO_VALUE if the graph did not have the property before
+     */
     Value graphRemoveProperty( int propertyKey );
 }

community/kernel-api/src/test/java/org/neo4j/internal/kernel/api/KernelAPIReadTestBase.java

@@ -28,8 +28,19 @@
 
 import org.neo4j.graphdb.GraphDatabaseService;
 
+/**
+ * KernelAPIReadTestBase is the basis of read tests targeting the Kernel API.
+ *
+ * As tests are packaged together with the API, they cannot provide all the functionality needed to construct the
+ * test graph, or provide the concrete Kernel to test. These things are abstracted behind the
+ * KernelAPIReadTestSupport interface, which needs to be implemented to test reading Kernel implementations.
+ *
+ * As read tests do not modify the graph, the test graph is created lazily on the first test run.
+ *
+ * @param <ReadSupport> The test support for the current test.
+ */
 @SuppressWarnings( "WeakerAccess" )
-public abstract class KernelAPIReadTestBase<G extends KernelAPIReadTestSupport>
+public abstract class KernelAPIReadTestBase<ReadSupport extends KernelAPIReadTestSupport>
 {
     protected static final TemporaryFolder folder = new TemporaryFolder();
     protected static KernelAPIReadTestSupport testSupport;
@@ -42,9 +53,9 @@ public abstract class KernelAPIReadTestBase<G extends KernelAPIReadTestSupport>
     protected Token token;
 
     /**
-     * Creates a new instance of KernelAPITestSupport, which will be used to execute the concrete test
+     * Creates a new instance of KernelAPIReadTestSupport, which will be used to execute the concrete test
      */
-    public abstract G newTestSupport();
+    public abstract ReadSupport newTestSupport();
 
     /**
      * Create the graph which all test in the class will be executed against. The graph is only built once,
@@ -65,7 +76,6 @@ public void setupGraph() throws IOException
         }
         Kernel kernel = testSupport.kernelToTest();
         session = kernel.beginSession( PermissionsFixture.allPermissions() );
-        testSupport.beforeEachTest();
         cursors = kernel.cursors();
         tx = session.beginTransaction();
         token = session.token();

community/kernel-api/src/test/java/org/neo4j/internal/kernel/api/KernelAPIReadTestSupport.java

@@ -25,13 +25,30 @@
 
 import org.neo4j.graphdb.GraphDatabaseService;
 
+/**
+ * This interface defines the functionality that's needed to run Kernel API Read tests (tests that extends
+ * KernelAPIReadTestBase) on a Kernel.
+ */
 public interface KernelAPIReadTestSupport
 {
+    /**
+     * Setup the test. Called once. Starts a Kernel in the provided store directory, and populates the graph using
+     * the provided create method.
+     *
+     * @param storeDir The directory in which to create the database.
+     * @param create Method which populates the database.
+     * @throws IOException If database creation failed due to IO problems.
+     */
     void setup( File storeDir, Consumer<GraphDatabaseService> create ) throws IOException;
 
-    void beforeEachTest();
-
+    /**
+     * The Kernel to test. Called before every test.
+     * @return The Kernel.
+     */
     Kernel kernelToTest();
 
+    /**
+     * Teardown the Kernel and any other resources once all tests have completed.
+     */
     void tearDown();
 }

community/kernel-api/src/test/java/org/neo4j/internal/kernel/api/KernelAPIWriteTestBase.java

@@ -28,8 +28,19 @@
 
 import org.neo4j.graphdb.GraphDatabaseService;
 
+/**
+ * KernelAPIWriteTestBase is the basis of write tests targeting the Kernel API.
+ *
+ * Just as with KernelAPIReadTestBase, write tests cannot provide all the functionality needed to construct the
+ * test kernel, and also do not know how to assert the effects of the writes. These things are abstracted behind the
+ * KernelAPIWriteTestSupport interface, which needs to be implemented to test Kernel write implementations.
+ *
+ * Since write tests modify the graph, the test graph is recreated on every test run.
+ *
+ * @param <WriteSupport> The test support for the current test.
+ */
 @SuppressWarnings( "WeakerAccess" )
-public abstract class KernelAPIWriteTestBase<G extends KernelAPIWriteTestSupport>
+public abstract class KernelAPIWriteTestBase<WriteSupport extends KernelAPIWriteTestSupport>
 {
     protected static final TemporaryFolder folder = new TemporaryFolder();
     protected static KernelAPIWriteTestSupport testSupport;
@@ -38,9 +49,9 @@ public abstract class KernelAPIWriteTestBase<G extends KernelAPIWriteTestSupport
     protected static GraphDatabaseService graphDb;
 
     /**
-     * Creates a new instance of KernelAPITestSupport, which will be used to execute the concrete test
+     * Creates a new instance of WriteSupport, which will be used to execute the concrete test
      */
-    public abstract G newTestSupport();
+    public abstract WriteSupport newTestSupport();
 
     @Before
     public void setupGraph() throws IOException
@@ -52,7 +63,7 @@ public void setupGraph() throws IOException
             testSupport.setup( folder.getRoot() );
             graphDb = testSupport.graphBackdoor();
         }
-        testSupport.beforeEachTest();
+        testSupport.clearGraph();
         Kernel kernel = testSupport.kernelToTest();
         session = kernel.beginSession( PermissionsFixture.allPermissions() );
         cursors = kernel.cursors();

community/kernel-api/src/test/java/org/neo4j/internal/kernel/api/KernelAPIWriteTestSupport.java

@@ -24,18 +24,37 @@
 
 import org.neo4j.graphdb.GraphDatabaseService;
 
+
+/**
+ * This interface defines the functionality that's needed to run Kernel API Write tests (tests that extends
+ * KernelAPIWriteTestBase) on a Kernel.
+ */
 public interface KernelAPIWriteTestSupport
 {
+    /**
+     * Create the Kernel to test in the provided directory.
+     * @param storeDir The directory to hold the database
+     * @throws IOException Thrown on IO failure during database creation
+     */
     void setup( File storeDir ) throws IOException;
 
-    void beforeEachTest();
+    /**
+     * Clear the graph. Executed before each test.
+     */
+    void clearGraph();
 
+    /**
+     * Return the Kernel to test. Executed before each test.
+     */
     Kernel kernelToTest();
 
     /**
      * Backdoor to allow asserting on write effects
      */
     GraphDatabaseService graphBackdoor();
 
+    /**
+     * Clean up resources and close the database. Executed after all tests are completed.
+     */
     void tearDown();
 }

community/kernel/src/test/java/org/neo4j/kernel/impl/newapi/ReadTestSupport.java

@@ -40,11 +40,6 @@ public void setup( File storeDir, Consumer<GraphDatabaseService> create ) throws
         create.accept( db );
     }
 
-    @Override
-    public void beforeEachTest()
-    {
-    }
-
     @Override
     public Kernel kernelToTest()
     {