Could not load TestContextBootstrapper [null].

错误日志：

java.lang.IllegalStateException: Could not load TestContextBootstrapper [null]. Specify @BootstrapWith's 'value' attribute or make the default bootstrapper class available.

	at org.springframework.test.context.BootstrapUtils.resolveTestContextBootstrapper(BootstrapUtils.java:145)
	at org.springframework.test.context.TestContextManager.<init>(TestContextManager.java:124)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTestContextManager(SpringJUnit4ClassRunner.java:151)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.<init>(SpringJUnit4ClassRunner.java:142)
	at org.springframework.test.context.junit4.SpringRunner.<init>(SpringRunner.java:49)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:104)
	at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:86)
	at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
	at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
	at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
	at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:33)
	at org.junit.internal.requests.FilterRequest.getRunner(FilterRequest.java:36)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:49)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.NoSuchMethodError: org.springframework.util.Assert.state(ZLjava/util/function/Supplier;)V
	at org.springframework.test.context.BootstrapUtils.resolveExplicitTestContextBootstrapper(BootstrapUtils.java:157)
	at org.springframework.test.context.BootstrapUtils.resolveTestContextBootstrapper(BootstrapUtils.java:128)
	... 19 more

导致原因：

spring-test版本冲突与spring 其他包版本不一致，如下图：

解决办法：

检查pom.xml文件。找到spring-test的依赖改为与boot相同的版本