diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad7101b5ba..ce6e71377f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -57,6 +57,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Updated PSDM to version 5.1.0 [#835](https://github.com/ie3-institute/simona/issues/835)
 - Refactor `WeatherSource` and `WeatherSourceWrapper` [#180](https://github.com/ie3-institute/simona/issues/180)
 - Remove unnecessary dependency `pekko-connectors-csv` [#857](https://github.com/ie3-institute/simona/issues/857)
+- 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)
diff --git a/src/test/groovy/edu/ie3/simona/model/grid/RefSystemTest.groovy b/src/test/groovy/edu/ie3/simona/model/grid/RefSystemTest.groovy
deleted file mode 100644
index 9ca17976a5..0000000000
--- a/src/test/groovy/edu/ie3/simona/model/grid/RefSystemTest.groovy
+++ /dev/null
@@ -1,74 +0,0 @@
-/*
- * © 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 edu.ie3.util.scala.quantities.Sq
-import spock.lang.Specification
-import squants.Dimensionless
-import squants.Each$
-import squants.electro.Amperes$
-import squants.electro.ElectricPotential
-import squants.electro.Kilovolts$
-import squants.electro.Ohms$
-import squants.electro.Volts$
-import squants.energy.Megawatts$
-import squants.energy.Watts$
-import squants.energy.Power
-
-
-class RefSystemTest extends Specification {
-
-  def "A RefSystem with nominal power and nominal voltage should provide corresponding nominal current and nominal impedance "() {
-
-    given: "the nominal power and the nominal voltage"
-
-    double nominalPower = 600000 // in voltampere
-    double nominalVoltage = 10000 // in volt
-
-    Power nominalPowerAsSquant = Sq.create(nominalPower, Watts$.MODULE$)
-    ElectricPotential nominalVoltageAsSquant = Sq.create(nominalVoltage, Volts$.MODULE$)
-
-    when:
-    RefSystem refSystem = RefSystem.apply(nominalPowerAsSquant, nominalVoltageAsSquant)
-
-    then: "the nominal current and the nominal power should be calculated accordingly"
-    refSystem.nominalPower() == Sq.create(600000d, Watts$.MODULE$)
-    refSystem.nominalVoltage() == Sq.create(10000d, Volts$.MODULE$)
-    refSystem.nominalCurrent() =~ Sq.create(34.64101615137754774109785366023500d, Amperes$.MODULE$)
-    refSystem.nominalImpedance() =~ Sq.create (166.6666666666666666666666666666666d, Ohms$.MODULE$)
-  }
-
-  def "A dimensionless impedance is transferred correctly between reference systems"() {
-    given:
-    RefSystem from = RefSystem.apply(Sq.create(60d, Megawatts$.MODULE$), Sq.create(110d, Kilovolts$.MODULE$))
-    RefSystem to = RefSystem.apply(Sq.create(40d, Megawatts$.MODULE$), Sq.create(110d, Kilovolts$.MODULE$))
-    Dimensionless impedance = Sq.create(0.1d, Each$.MODULE$)
-    Dimensionless expected = Sq.create(0.06666666666666667d, Each$.MODULE$)
-
-    when:
-    Dimensionless actual = RefSystem.transferImpedance(impedance, from, to)
-
-    then:
-    actual =~ expected
-  }
-
-  def "A dimensionless admittance is transferred correctly between reference systems"() {
-    given:
-    RefSystem from = RefSystem.apply(Sq.create(60d, Megawatts$.MODULE$), Sq.create(110d, Kilovolts$.MODULE$))
-    RefSystem to = RefSystem.apply(Sq.create(40d, Megawatts$.MODULE$), Sq.create(110d, Kilovolts$.MODULE$))
-    Dimensionless admittance = Sq.create(0.1d, Each$.MODULE$)
-    Dimensionless expected = Sq.create(0.15000000000000002d, Each$.MODULE$)
-
-    when:
-    Dimensionless actual = RefSystem.transferAdmittance(admittance, from, to)
-
-    then:
-
-    actual =~ expected
-  }
-}
diff --git a/src/test/scala/edu/ie3/simona/model/grid/RefSystemSpec.scala b/src/test/scala/edu/ie3/simona/model/grid/RefSystemSpec.scala
new file mode 100644
index 0000000000..38aed79d1d
--- /dev/null
+++ b/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 nominalPower: Power = Kilowatts(600)
+    val nominalVoltage: ElectricPotential = Kilovolts(10)
+
+    val refSystem = RefSystem(nominalPower, nominalVoltage)
+
+    refSystem.nominalPower should be(nominalPower)
+    refSystem.nominalVoltage should be(nominalVoltage)
+    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)
+  }
+}