Add SNAPSHOTs tests to CI

Fixes: gh-5129

Jenkinsfile

@@ -53,6 +53,19 @@ try {
 				}
 			}
 		}
+	},
+	snapshots: {
+		stage('Snapshot Tests') {
+			node {
+				checkout scm
+				try {
+					sh "./gradlew clean test -PspringVersion='5.+' -PreactorVersion=Bismuth-BUILD-SNAPSHOT -PspringDataVersion=Kay-BUILD-SNAPSHOT --refresh-dependencies --no-daemon --stacktrace"
+				} catch(Exception e) {
+					currentBuild.result = 'FAILED: snapshots'
+					throw e
+				}
+			}
+		}
 	}
 
 	if(currentBuild.result == 'SUCCESS') {

gradle/dependency-management.gradle

@@ -1,8 +1,20 @@
+if (!project.hasProperty('reactorVersion')) {
+	ext.reactorVersion = 'Bismuth-SR7'
+}
+
+if (!project.hasProperty('springVersion')) {
+	ext.springVersion = '5.0.4.RELEASE'
+}
+
+if (!project.hasProperty('springDataVersion')) {
+	ext.springDataVersion = 'Kay-SR5'
+}
+
 dependencyManagement {
 	imports {
-		mavenBom 'io.projectreactor:reactor-bom:Bismuth-SR7'
-		mavenBom 'org.springframework:spring-framework-bom:5.0.4.RELEASE'
-		mavenBom 'org.springframework.data:spring-data-releasetrain:Kay-SR5'
+		mavenBom "io.projectreactor:reactor-bom:${reactorVersion}"
+		mavenBom "org.springframework:spring-framework-bom:${springVersion}"
+		mavenBom "org.springframework.data:spring-data-releasetrain:${springDataVersion}"
 	}
 	dependencies {
 		dependency 'cglib:cglib-nodep:3.2.6'