1 files changed, 90 insertions, 0 deletions
diff --git a/src/test/scala/chiselTests/util/random/PRNGSpec.scala b/src/test/scala/chiselTests/util/random/PRNGSpec.scala
new file mode 100644
index 00000000..138a6ceb
--- /dev/null
+++ b/src/test/scala/chiselTests/util/random/PRNGSpec.scala
@@ -0,0 +1,90 @@
+// See LICENSE for license details.
+
+package chiselTests.util.random
+
+import chisel3._
+import chisel3.testers.BasicTester
+import chisel3.util.Counter
+import chisel3.util.random.PRNG
+
+import chiselTests.ChiselFlatSpec
+
+class CyclePRNG(width: Int, seed: Option[BigInt], step: Int, updateSeed: Boolean)
+    extends PRNG(width, seed, step, updateSeed) {
+
+  def delta(s: UInt): UInt = s ## s(width - 1)
+
+}
+
+class PRNGStepTest extends BasicTester {
+
+  val count2: UInt = Counter(true.B, 2)._1
+  val count4: UInt = Counter(true.B, 4)._1
+
+  val a: UInt = PRNG(new CyclePRNG(16, Some(1), 1, false), true.B)
+  val b: UInt = PRNG(new CyclePRNG(16, Some(1), 2, false), count2 === 1.U)
+  val c: UInt = PRNG(new CyclePRNG(16, Some(1), 4, false), count4 === 3.U)
+
+  val (_, done) = Counter(true.B, 16)
+
+  when (count2 === 0.U) {
+    assert(a === b, "1-step and 2-step PRNGs did not agree! (0b%b != 0b%b)", a, b)
+  }
+
+  when (count4 === 0.U) {
+    assert(a === c, "1-step and 4-step PRNGs did not agree!")
+  }
+
+  when (done) {
+    stop()
+  }
+
+}
+
+class PRNGUpdateSeedTest(updateSeed: Boolean, seed: BigInt, expected: BigInt) extends BasicTester {
+
+  val a: CyclePRNG = Module(new CyclePRNG(16, Some(1), 1, updateSeed))
+
+  val (count, done) = Counter(true.B, 4)
+
+  a.io.increment := true.B
+  a.io.seed.valid := count === 2.U
+  a.io.seed.bits := seed.U
+
+  when (count === 3.U) {
+    assert(a.io.out === expected.U, "Output didn't match!")
+  }
+
+  when (done) {
+    stop()
+  }
+
+}
+
+class PRNGSpec extends ChiselFlatSpec {
+
+  behavior of "PRNG"
+
+  it should "throw an exception if the step size is < 1" in {
+    { the [IllegalArgumentException] thrownBy elaborate(new CyclePRNG(0, Some(1), 1, true)) }
+      .getMessage should include ("Width must be greater than zero!")
+  }
+
+  it should "throw an exception if the step size is <= 0" in {
+    { the [IllegalArgumentException] thrownBy elaborate(new CyclePRNG(1, Some(1), 0, true)) }
+      .getMessage should include ("Step size must be greater than one!")
+  }
+
+  it should "handle non-unary steps" in {
+    assertTesterPasses(new PRNGStepTest)
+  }
+
+  it should "handle state update without and with updateSeed enabled" in {
+    info("without updateSeed okay!")
+    assertTesterPasses(new PRNGUpdateSeedTest(false, 3, 3))
+
+    info("with updateSeed okay!")
+    assertTesterPasses(new PRNGUpdateSeedTest(true, 3, 6))
+  }
+
+}