Field Programmable Gate Arrays, or FPGAs, allow designers to implement hardware designs using hardware description languages (HDLs). This type of designs have been gaining significant popularity since improvements in clock frequencies, of high-end CPUs, have started to level off and other alternatives have been explored to accelerate computations. However, traditional HDLs lack a number of modern facilities and a rich ecosystem to express and test designs, which severely restricts the productivity of designers. In this paper, we propose ScalaHDL, an open-source domain-specific language (DSL) built on top of Scala, that enables designers to describe algorithms using a multi-paradigm programming language, and generate the required Verilog code to implement such systems. In addition, these designs can be simulated so that values can be tested programmatically using unit-tests. With ScalaHDL, designers can also leverage the rich and mature ecosystems provided by Java and Scala.