Rewrote RefSystemTest from groovy to scala.

CHANGELOG.md

@@ -54,6 +54,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Rewrote PVModelTest from groovy to scala [#646](https://github.com/ie3-institute/simona/issues/646)
 - Making configuration of `RefSystem` via config optional [#769](https://github.com/ie3-institute/simona/issues/769)
 - Updated PSDM to version 5.1.0 [#835](https://github.com/ie3-institute/simona/issues/835)
+- Rewrote RefSystemTest from groovy to scala [#646](https://github.com/ie3-institute/simona/issues/646)
 
 ### Fixed
 - Removed a repeated line in the documentation of vn_simona config [#658](https://github.com/ie3-institute/simona/issues/658)

src/test/scala/edu/ie3/simona/model/grid/RefSystemSpec.scala

@@ -0,0 +1,56 @@
+/*
+ * © 2020. TU Dortmund University,
+ * Institute of Energy Systems, Energy Efficiency and Energy Economics,
+ * Research group Distribution grid planning and operation
+ */
+
+package edu.ie3.simona.model.grid
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+import squants.{Dimensionless, Each}
+import squants.electro.{Amperes, ElectricPotential, Kilovolts, Ohms}
+import squants.energy.{Megawatts, Power, Kilowatts}
+
+class RefSystemSpec extends AnyFlatSpec with Matchers {
+
+  "A RefSystem with nominal power and nominal voltage" should "provide corresponding nominal current and nominal impedance" in {
+
+    val nominalPowerAsSquant: Power = Kilowatts(600)
+    val nominalVoltageAsSquant: ElectricPotential = Kilovolts(10)
+
+    val refSystem = RefSystem(nominalPowerAsSquant, nominalVoltageAsSquant)
+
+    refSystem.nominalPower should be(nominalPowerAsSquant)
+    refSystem.nominalVoltage should be(nominalVoltageAsSquant)
+    refSystem.nominalCurrent should be(
+      Amperes(34.64101615137754774109785366023500d)
+    )
+    refSystem.nominalImpedance should be(
+      Ohms(166.6666666666666666666666666666666d)
+    )
+  }
+
+  "A dimensionless impedance" should "be transferred correctly between reference systems" in {
+    val from = RefSystem(Megawatts(60d), Kilovolts(110d))
+    val to = RefSystem(Megawatts(40d), Kilovolts(110d))
+    val impedance = Each(0.1d)
+    val expected = Each(0.06666666666666667d)
+
+    val actual: Dimensionless = RefSystem.transferImpedance(impedance, from, to)
+
+    actual should be(expected)
+  }
+
+  "A dimensionless admittance" should "be transferred correctly between reference systems" in {
+    val from = RefSystem(Megawatts(60d), Kilovolts(110d))
+    val to = RefSystem(Megawatts(40d), Kilovolts(110d))
+    val admittance = Each(0.1d)
+    val expected = Each(0.15000000000000002d)
+
+    val actual: Dimensionless =
+      RefSystem.transferAdmittance(admittance, from, to)
+
+    actual should be(expected)
+  }
+}