diff --git a/src/test/scala/SimpleMultiplier.scala b/src/test/scala/SimpleMultiplier.scala
index 4fac7e8..d9b695c 100644
--- a/src/test/scala/SimpleMultiplier.scala
+++ b/src/test/scala/SimpleMultiplier.scala
@@ -24,66 +24,73 @@ class SimpleMultiplierUnitTester extends FlatSpec with ChiselScalatestTester wit
     multHigh(aSigned, bSigned)
   }
 
+  def mult32(a: BigInt, b: BigInt): BigInt = {
+    val a32 = a & BigInt("ffffffff", 16)
+    val b32 = b & BigInt("ffffffff", 16)
+
+    (a32 * b32)
+  }
+
+  def multHigh32(a: BigInt, b: BigInt): BigInt = {
+    val a32 = a & BigInt("ffffffff", 16)
+    val b32 = b & BigInt("ffffffff", 16)
+
+    val m = ((a32 * b32) >> 32) & BigInt("ffffffff", 16)
+    (m << 32) | m
+  }
+
+  def multHighSigned32(a: BigInt, b: BigInt): BigInt = {
+    val a32 = a & BigInt("ffffffff", 16)
+    val b32 = b & BigInt("ffffffff", 16)
+    val aSigned = if (a32.testBit(31)) (BigInt("ffffffff", 16) << 32) + a32 else a32
+    val bSigned = if (b32.testBit(31)) (BigInt("ffffffff", 16) << 32) + b32 else b32
+
+    val m = ((aSigned * bSigned) >> 32) & BigInt("ffffffff", 16)
+    (m << 32) | m
+  }
+
+  def runOneTest(m: SimpleMultiplier, mult: (BigInt, BigInt) => BigInt) = {
+    for ((x, y) <- tests) {
+      while (m.io.in.ready.peek().litToBoolean == false) {
+        m.clock.step(1)
+      }
+
+      m.io.in.bits.a.poke(x.U)
+      m.io.in.bits.b.poke(y.U)
+      m.io.in.valid.poke(true.B)
+      m.clock.step(1)
+      m.io.in.valid.poke(false.B)
+
+      while (m.io.out.valid.peek().litToBoolean == false) {
+        m.clock.step(1)
+      }
+
+      m.io.out.bits.expect(mult(x, y).U)
+    }
+  }
+
   it should "pass a unit test" in {
     test(new SimpleMultiplier(64)) { m =>
-      for ((x, y) <- tests) {
-        while (m.io.in.ready.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
 
-        m.io.in.bits.a.poke(x.U)
-        m.io.in.bits.b.poke(y.U)
-        m.io.in.valid.poke(true.B)
-        m.clock.step(1)
-        m.io.in.valid.poke(false.B)
-
-        while (m.io.out.valid.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
-
-        m.io.out.bits.expect(mult(x, y).U)
-      }
+      runOneTest(m, mult)
 
       m.io.in.bits.high.poke(true.B)
-
-      for ((x, y) <- tests) {
-        while (m.io.in.ready.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
-
-        m.io.in.bits.a.poke(x.U)
-        m.io.in.bits.b.poke(y.U)
-        m.io.in.valid.poke(true.B)
-        m.clock.step(1)
-        m.io.in.valid.poke(false.B)
-
-        while (m.io.out.valid.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
-
-        m.io.out.bits.expect(multHigh(x, y).U)
-      }
+      runOneTest(m, multHigh)
 
       m.io.in.bits.signed.poke(true.B)
+      runOneTest(m, multHighSigned)
 
-      for ((x, y) <- tests) {
-        while (m.io.in.ready.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
+      m.io.in.bits.signed.poke(false.B)
+      m.io.in.bits.high.poke(false.B)
 
-        m.io.in.bits.a.poke(x.U)
-        m.io.in.bits.b.poke(y.U)
-        m.io.in.valid.poke(true.B)
-        m.clock.step(1)
-        m.io.in.valid.poke(false.B)
+      m.io.in.bits.is32bit.poke(true.B)
+      runOneTest(m, mult32)
 
-        while (m.io.out.valid.peek().litToBoolean == false) {
-          m.clock.step(1)
-        }
-
-        m.io.out.bits.expect(multHighSigned(x, y).U)
-      }
+      m.io.in.bits.high.poke(true.B)
+      runOneTest(m, multHigh32)
 
+      m.io.in.bits.signed.poke(true.B)
+      runOneTest(m, multHighSigned32)
     }
   }
 }