Add tests for link builder

hapi-fhir-server-mdm/src/test/java/ca/uhn/fhir/mdm/api/paging/MdmPageLinkBuilderTest.java

@@ -0,0 +1,37 @@
+package ca.uhn.fhir.mdm.api.paging;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.jupiter.api.Assertions.*;
+
+class MdmPageLinkBuilderTest {
+
+	@Test
+	void buildLinkWithExistingParameters() {
+		//Given
+		String expected = "http://localhost:8000/$mdm-query-links?sourceResourceId=Patient/123&_offset=1&_count=1";
+		String baseUrl = "http://localhost:8000/$mdm-query-links?sourceResourceId=Patient/123";
+
+		//When
+		String builtUrl = MdmPageLinkBuilder.buildLinkWithOffsetAndCount(baseUrl, 1, 1);
+
+		//Then
+		assertThat(builtUrl, is(equalTo(expected)));
+	}
+
+	@Test
+	void buildLinkWithoutExistingParameters() {
+		//Given
+		String expected = "http://localhost:8000/$mdm-query-links?_offset=1&_count=1";
+		String baseUrl = "http://localhost:8000/$mdm-query-links";
+
+		//When
+		String builtUrl = MdmPageLinkBuilder.buildLinkWithOffsetAndCount(baseUrl, 1, 1);
+
+		//Then
+		assertThat(builtUrl, is(equalTo(expected)));
+	}
+}