If Verilator is not installed, running sbt test will fail on dsptools.numbers.BlackBoxFloatSpec.

Doing operations like a+b may fail with mysterious error messages like [error] found : T [error] required: String If dsptools.numbers.implicits._ (the _ at the end is important!) is not imported, then the implicit conversion that converts a+b to Ring[T].plus(a,b) won't be in scope and the compiler assumes a+b means a.toString + b, which is not what you want.

Real number tests are failing when testing with backend. If this is associated with a warning message like

WARNING: external module "BBFAdd"(BBFAdd:BBFAdd)was not matched with an implementation

a likely problem is that the wrong Driver is being called. For DspReals to work the interpreter must be given the black box factory code. The dsptools.Driver does this by default, using the iotesters.Driver. Check to see that the tests employ the correct Driver. For example:

    chisel3.iotesters.Driver(() => new RealAdder, "firrtl") { c =>

should be

    dsptools.Driver.execute(() => new RealAdder, Array("--backend-name", "firrtl")) { c =>