Add nullability annotations to tests in module/spring-boot-http-converter

See gh-47263

Author: mhalbritter

module/spring-boot-http-converter/build.gradle

@@ -50,3 +50,7 @@ dependencies {
 testRuntimeOnly("org.springframework:spring-webflux")
 testRuntimeOnly("tools.jackson.dataformat:jackson-dataformat-cbor")
 }
+
+tasks.named("compileTestJava") {
+options.nullability.checking = "tests"
+}

module/spring-boot-http-converter/src/test/java/org/springframework/boot/http/converter/autoconfigure/HttpMessageConvertersTests.java

@@ -21,6 +21,7 @@
 import java.util.List;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.http.converter.ByteArrayHttpMessageConverter;
@@ -172,10 +173,12 @@ protected List<HttpMessageConverter<?>> postProcessPartConverters(
 
 private List<HttpMessageConverter<?>> extractFormPartConverters(List<HttpMessageConverter<?>> converters) {
 AllEncompassingFormHttpMessageConverter formConverter = findFormConverter(converters);
+assertThat(formConverter).isNotNull();
 return formConverter.getPartConverters();
 }
 
-private AllEncompassingFormHttpMessageConverter findFormConverter(Collection<HttpMessageConverter<?>> converters) {
+private @Nullable AllEncompassingFormHttpMessageConverter findFormConverter(
+Collection<HttpMessageConverter<?>> converters) {
 for (HttpMessageConverter<?> converter : converters) {
 if (converter instanceof AllEncompassingFormHttpMessageConverter allEncompassingConverter) {
 return allEncompassingConverter;