diff --git a/module/spring-boot-micrometer-tracing/build.gradle b/module/spring-boot-micrometer-tracing/build.gradle
index 1c29e3c5a7f..4d07b99375a 100644
--- a/module/spring-boot-micrometer-tracing/build.gradle
+++ b/module/spring-boot-micrometer-tracing/build.gradle
@@ -66,3 +66,11 @@ dependencies {
 	testRuntimeOnly("ch.qos.logback:logback-classic")
 	testRuntimeOnly("io.grpc:grpc-api")
 }
+
+tasks.named("compileTestJava") {
+	options.nullability.checking = "tests"
+}
+
+tasks.named("compileDockerTestJava") {
+	options.nullability.checking = "tests"
+}
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositePropagationFactoryTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositePropagationFactoryTests.java
index 76a427bc1f1..92fcd33e8e0 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositePropagationFactoryTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositePropagationFactoryTests.java
@@ -24,6 +24,7 @@ import java.util.Map;
 import brave.propagation.Propagation;
 import brave.propagation.TraceContext;
 import brave.propagation.TraceContextOrSamplingFlags;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
@@ -92,7 +93,9 @@ class CompositePropagationFactoryTests {
 			Propagation<String> propagation = factory.get();
 			Map<String, String> request = Map.of("a", "a-value", "b", "b-value");
 			TraceContextOrSamplingFlags context = propagation.extractor(new MapGetter()).extract(request);
-			assertThat(context.context().extra()).containsExactly("a");
+			TraceContext traceContext = context.context();
+			assertThat(traceContext).isNotNull();
+			assertThat(traceContext.extra()).containsExactly("a");
 		}
 
 		@Test
@@ -127,7 +130,7 @@ class CompositePropagationFactoryTests {
 	private static final class MapGetter implements Propagation.Getter<Map<String, String>, String> {
 
 		@Override
-		public String get(Map<String, String> request, String key) {
+		public @Nullable String get(Map<String, String> request, String key) {
 			return request.get(key);
 		}
 
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositeTextMapPropagatorTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositeTextMapPropagatorTests.java
index 193919322c5..f89bd7e2122 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositeTextMapPropagatorTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/CompositeTextMapPropagatorTests.java
@@ -29,6 +29,7 @@ import io.opentelemetry.context.propagation.TextMapGetter;
 import io.opentelemetry.context.propagation.TextMapPropagator;
 import io.opentelemetry.context.propagation.TextMapSetter;
 import io.opentelemetry.extension.trace.propagation.B3Propagator;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.InOrder;
@@ -147,7 +148,7 @@ class CompositeTextMapPropagatorTests {
 		}
 
 		@Override
-		public String get(Map<String, String> carrier, String key) {
+		public @Nullable String get(@Nullable Map<String, String> carrier, String key) {
 			if (carrier == null) {
 				return null;
 			}
@@ -173,12 +174,12 @@ class CompositeTextMapPropagatorTests {
 		}
 
 		@Override
-		public <C> void inject(Context context, C carrier, TextMapSetter<C> setter) {
+		public <C> void inject(Context context, @Nullable C carrier, TextMapSetter<C> setter) {
 			setter.set(carrier, this.field, this.field + "-value");
 		}
 
 		@Override
-		public <C> Context extract(Context context, C carrier, TextMapGetter<C> getter) {
+		public <C> Context extract(Context context, @Nullable C carrier, TextMapGetter<C> getter) {
 			String value = getter.get(carrier, this.field);
 			if (value != null) {
 				return context.with(this.contextKeyRegistry.get(this.field), value);
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/LocalBaggageFieldsTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/LocalBaggageFieldsTests.java
index ac442cc60ff..8071e699342 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/LocalBaggageFieldsTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/LocalBaggageFieldsTests.java
@@ -25,6 +25,7 @@ import brave.propagation.Propagation.Factory;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
 
 /**
  * Tests for {@link LocalBaggageFields}.
@@ -52,8 +53,9 @@ class LocalBaggageFieldsTests {
 	private static FactoryBuilder createBuilder() {
 		return BaggagePropagation.newFactoryBuilder(new Factory() {
 			@Override
+			@SuppressWarnings("unchecked")
 			public Propagation<String> get() {
-				return null;
+				return mock(Propagation.class);
 			}
 		});
 	}
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/MicrometerTracingAutoConfigurationTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/MicrometerTracingAutoConfigurationTests.java
index 40966034580..b59e8086221 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/MicrometerTracingAutoConfigurationTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/MicrometerTracingAutoConfigurationTests.java
@@ -275,7 +275,8 @@ class MicrometerTracingAutoConfigurationTests {
 
 		@Bean
 		SpanTagAnnotationHandler spanTagAnnotationHandler() {
-			return new SpanTagAnnotationHandler((valueResolverClass) -> null, (valueExpressionResolverClass) -> null);
+			return new SpanTagAnnotationHandler((valueResolverClass) -> mock(ValueResolver.class),
+					(valueExpressionResolverClass) -> mock(ValueExpressionResolver.class));
 		}
 
 	}
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/prometheus/LazyTracingSpanContextTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/prometheus/LazyTracingSpanContextTests.java
index 1e3eb0c588c..b7a6d7e48eb 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/prometheus/LazyTracingSpanContextTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/prometheus/LazyTracingSpanContextTests.java
@@ -19,6 +19,7 @@ package org.springframework.boot.micrometer.tracing.autoconfigure.prometheus;
 import io.micrometer.tracing.Span;
 import io.micrometer.tracing.TraceContext;
 import io.micrometer.tracing.Tracer;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.BeansException;
@@ -46,7 +47,7 @@ class LazyTracingSpanContextTests {
 		}
 
 		@Override
-		public Tracer getObject(Object... args) throws BeansException {
+		public Tracer getObject(@Nullable Object... args) throws BeansException {
 			return LazyTracingSpanContextTests.this.tracer;
 		}
 
diff --git a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/zipkin/ZipkinConfigurationsBraveConfigurationTests.java b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/zipkin/ZipkinConfigurationsBraveConfigurationTests.java
index 2a5429a436b..9ee2fa0673e 100644
--- a/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/zipkin/ZipkinConfigurationsBraveConfigurationTests.java
+++ b/module/spring-boot-micrometer-tracing/src/test/java/org/springframework/boot/micrometer/tracing/autoconfigure/zipkin/ZipkinConfigurationsBraveConfigurationTests.java
@@ -22,6 +22,7 @@ import brave.Tag;
 import brave.handler.MutableSpan;
 import brave.handler.SpanHandler;
 import brave.propagation.TraceContext;
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
 import zipkin2.reporter.BytesEncoder;
 import zipkin2.reporter.BytesMessageSender;
@@ -186,7 +187,7 @@ class ZipkinConfigurationsBraveConfigurationTests {
 		Tag<Throwable> throwableTag() {
 			return new Tag<>("exception") {
 				@Override
-				protected String parseValue(Throwable throwable, TraceContext traceContext) {
+				protected @Nullable String parseValue(Throwable throwable, @Nullable TraceContext traceContext) {
 					return throwable.getMessage();
 				}
 			};