Tests: add basic link condition tests objectbox/objectbox#934

Author: greenrobot-team

tests/objectbox-java-test/src/test/java/io/objectbox/relation/AbstractRelationTest.java

@@ -55,9 +55,16 @@ public void initBoxes() {
         orderBox.removeAll();
     }
 
+    /**
+     * Puts customer Joe.
+     */
     protected Customer putCustomer() {
+        return putCustomer("Joe");
+    }
+
+    Customer putCustomer(String name) {
         Customer customer = new Customer();
-        customer.setName("Joe");
+        customer.setName(name);
         customerBox.put(customer);
         return customer;
     }

tests/objectbox-java-test/src/test/java/io/objectbox/relation/LinkQueryTest.java

@@ -0,0 +1,56 @@
+package io.objectbox.relation;
+
+import io.objectbox.query.Query;
+import io.objectbox.query.QueryBuilder;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+/**
+ * Tests link conditions for queries to filter on related entities.
+ * <p>
+ * There are more extensive tests in integration tests.
+ */
+public class LinkQueryTest extends AbstractRelationTest {
+
+    @Test
+    public void link_withRegularCondition() {
+        Customer john = putCustomer("John");
+        putOrder(john, "Apples");
+        putOrder(john, "Oranges");
+
+        Customer alice = putCustomer("Alice");
+        putOrder(alice, "Apples");
+        putOrder(alice, "Bananas");
+
+        // link condition matches orders from Alice
+        // simple regular condition matches single order for both
+        QueryBuilder<Order> builder = orderBox
+                .query(Order_.text.equal("Apples"));
+        builder.link(Order_.customer)
+                .apply(Customer_.name.equal("Alice").alias("name"));
+
+        try (Query<Order> query = builder.build()) {
+            Order order = query.findUnique();
+            assertNotNull(order);
+            assertEquals("Apples", order.getText());
+            assertEquals("Alice", order.getCustomer().getTarget().getName());
+        }
+
+        // link condition matches orders from Alice
+        // complex regular conditions matches two orders for John, one for Alice
+        QueryBuilder<Order> builderComplex = orderBox
+                .query(Order_.text.equal("Apples").or(Order_.text.equal("Oranges")));
+        builderComplex.link(Order_.customer)
+                .apply(Customer_.name.equal("Alice"));
+
+        try (Query<Order> query = builderComplex.build()) {
+            Order order = query.findUnique();
+            assertNotNull(order);
+            assertEquals("Apples", order.getText());
+            assertEquals("Alice", order.getCustomer().getTarget().getName());
+        }
+    }
+
+}