Consistently support no value params in query string

Closes gh-35329

spring-test/src/main/java/org/springframework/test/web/servlet/request/AbstractMockHttpServletRequestBuilder.java

@@ -911,10 +911,12 @@ public abstract class AbstractMockHttpServletRequestBuilder<B extends AbstractMo
 	}
 
 	private void addRequestParams(MockHttpServletRequest request, MultiValueMap<String, String> map) {
-		map.forEach((key, values) -> values.forEach(value -> {
-			value = (value != null ? UriUtils.decode(value, StandardCharsets.UTF_8) : null);
-			request.addParameter(UriUtils.decode(key, StandardCharsets.UTF_8), value);
-		}));
+		map.forEach((key, values) ->
+				request.addParameter(
+						UriUtils.decode(key, StandardCharsets.UTF_8),
+						values.stream()
+								.map(value -> value != null ? UriUtils.decode(value, StandardCharsets.UTF_8) : null)
+								.toArray(String[]::new)));
 	}
 
 	private byte[] writeFormData(MediaType mediaType, Charset charset) {

spring-test/src/test/java/org/springframework/test/web/servlet/request/MockHttpServletRequestBuilderTests.java

@@ -311,6 +311,15 @@ class MockHttpServletRequestBuilderTests {
 		assertThat(request.getParameterMap().get("foo")).containsExactly();
 	}
 
+	@Test // gh-35210
+	void queryStringWithoutValues() {
+		this.builder = new MockHttpServletRequestBuilder(GET).uri("/path?foo");
+		MockHttpServletRequest request = this.builder.buildRequest(this.servletContext);
+
+		assertThat(request.getQueryString()).isEqualTo("foo");
+		assertThat(request.getParameterMap().get("foo")).containsExactly((String) null);
+	}
+
 	@Test
 	void formField() {
 		this.builder = new MockHttpServletRequestBuilder(POST).uri("/");