Add dependency on JUnit Vintage TestEngine for IDEA

This commit introduces an explicit dependency on the latest JUnit
Vintage TestEngine so that it overrides whatever is bundled by
default in IntelliJ IDEA.

This allows for a more seamless upgrade to newer versions of JUnit 5 and
the JUnit Platform before IDEA has been officially updated to support
those versions, while simultaneously allowing developers to continue
to execute JUnit 4 based tests within IDEA.

build.gradle

@@ -72,6 +72,7 @@ configure(allprojects) { project ->
 	ext.jspVersion             = "2.3.2-b02"
 	ext.jtaVersion             = "1.2"
 	ext.junitVersion           = "4.12"
+	ext.junitVintageVersion    = "4.12.0-M4"
 	ext.junitJupiterVersion    = '5.0.0-M4'
 	ext.junitPlatformVersion   = '1.0.0-M4'
 	ext.log4jVersion           = '2.8.2'
@@ -1086,9 +1087,10 @@ project("spring-test") {
 		testCompile('de.bechte.junit:junit-hierarchicalcontextrunner:4.12.1')
 		testCompile('io.projectreactor.ipc:reactor-netty')
 		testRuntime("org.junit.jupiter:junit-jupiter-engine:${junitJupiterVersion}")
-		// Pull in the latest Launcher API so that it overrides whatever
-		// is bundled by default in IntelliJ IDEA.
+		// Pull in the latest Launcher API and the Vintage engine so
+		// that we can run JUnit 4 tests in IntelliJ IDEA.
 		testRuntime("org.junit.platform:junit-platform-launcher:${junitPlatformVersion}")
+		testRuntime("org.junit.vintage:junit-vintage-engine:${junitVintageVersion}")
 		testRuntime("org.apache.logging.log4j:log4j-jul:${log4jVersion}")  // Java Util Logging for JUnit 5
 		testRuntime("org.ehcache:ehcache:${ehcache3Version}")
 		testRuntime("org.terracotta:management-model:2.0.0")