scalacheck 1.13.x is not compatible with scalatest 2.2.6. See: typelevel/scalacheck#217

Sam Smoot · Sam Smoot · commit eaf070b9a5f9 · 2016-04-20T16:25:37.000-05:00
diff --git a/build.sbt b/build.sbt
@@ -55,7 +55,7 @@ lazy val core: Project = (project in file("core"))
       "com.typesafe.akka" %% "akka-http-core" % akkaVersion,
       "com.typesafe.akka" %% "akka-http-experimental" % akkaVersion,
       "com.typesafe.akka" %% "akka-http-testkit" % akkaVersion % "test",
-      "org.scalacheck" %% "scalacheck" % "1.13.0" % "test",
+      "org.scalacheck" %% "scalacheck" % "1.12.5" % "test",
       scalaTest
     )
   )

Original file line number	Diff line number	Diff line change
`@@ -55,7 +55,7 @@ lazy val core: Project = (project in file("core"))`
`55`	`55`	`"com.typesafe.akka" %% "akka-http-core" % akkaVersion,`
`56`	`56`	`"com.typesafe.akka" %% "akka-http-experimental" % akkaVersion,`
`57`	`57`	`"com.typesafe.akka" %% "akka-http-testkit" % akkaVersion % "test",`
`58`		`- "org.scalacheck" %% "scalacheck" % "1.13.0" % "test",`
	`58`	`+ "org.scalacheck" %% "scalacheck" % "1.12.5" % "test",`
`59`	`59`	`scalaTest`
`60`	`60`	`)`
`61`	`61`	`)`