2 files changed, 28 insertions, 0 deletions
diff --git a/src/test/resources/features/HasLoops.fir b/src/test/resources/features/HasLoops.fir
new file mode 100644
index 00000000..e238761d
--- /dev/null
+++ b/src/test/resources/features/HasLoops.fir
@@ -0,0 +1,9 @@
+circuit HasLoops :
+  module HasLoops :
+    input i : UInt<1>
+    output o : UInt<1>
+    wire a : UInt<1>
+    wire b : UInt<1>
+    a <= and(b,i)
+    b <= not(a)
+    o <= add(a, UInt(1))
diff --git a/src/test/scala/firrtlTests/CheckCombLoopsSpec.scala b/src/test/scala/firrtlTests/CheckCombLoopsSpec.scala
index dfb61843..2c12d4ca 100644
--- a/src/test/scala/firrtlTests/CheckCombLoopsSpec.scala
+++ b/src/test/scala/firrtlTests/CheckCombLoopsSpec.scala
@@ -8,6 +8,8 @@ import firrtl.passes._
 import firrtl.transforms._
 import firrtl.Mappers._
 import annotations._
+import java.io.File
+import java.nio.file.Paths
 
 class CheckCombLoopsSpec extends SimpleTransformSpec {
 
@@ -147,5 +149,22 @@ class CheckCombLoopsSpec extends SimpleTransformSpec {
       compile(CircuitState(parse(input), ChirrtlForm, None), writer)
     }
   }
+}
+
+class CheckCombLoopsCommandLineSpec extends FirrtlFlatSpec {
 
+  val testDir = createTestDirectory("CombLoopChecker")
+  val inputFile = Paths.get(getClass.getResource("/features/HasLoops.fir").toURI()).toFile()
+  val outFile = new File(testDir, "HasLoops.v")
+  val args = Array("-i", inputFile.getAbsolutePath, "-o", outFile.getAbsolutePath, "-X", "verilog")
+
+  "Combinational loops detection" should "run by default" in {
+    a [CheckCombLoops.CombLoopException] should be thrownBy {
+      firrtl.Driver.execute(args)
+    }
+  }
+
+  it should "not run when given --no-check-comb-loops option" in {
+    firrtl.Driver.execute(args :+ "--no-check-comb-loops")
+  }
 }