Add milliwatt hour energy unit (mWh) (#284)

shared/src/main/scala/squants/energy/Energy.scala

@@ -53,6 +53,7 @@ final class Energy private (val value: Double, val unit: EnergyUnit)
   def /(that: PowerRamp): TimeSquared = (this / that.timeIntegrated) * time
 
   def toWattHours = to(WattHours)
+  def toMilliwattHours = to(MilliwattHours)
   def toKilowattHours = to(KilowattHours)
   def toMegawattHours = to(MegawattHours)
   def toGigawattHours = to(GigawattHours)
@@ -99,7 +100,7 @@ object Energy extends Dimension[Energy] {
   def name = "Energy"
   def primaryUnit = WattHours
   def siUnit = Joules
-  def units = Set(WattHours, KilowattHours, MegawattHours, GigawattHours,
+  def units = Set(WattHours, MilliwattHours, KilowattHours, MegawattHours, GigawattHours,
     Joules, Picojoules, Nanojoules, Microjoules, Millijoules,
     Kilojoules, Megajoules, Gigajoules, Terajoules,
     BritishThermalUnits, MBtus, MMBtus, Ergs,
@@ -118,6 +119,11 @@ object WattHours extends EnergyUnit with PrimaryUnit {
   val symbol = "Wh"
 }
 
+object MilliwattHours extends EnergyUnit {
+  val conversionFactor = Watts.conversionFactor * MetricSystem.Milli
+  val symbol = "mWh"
+}
+
 object KilowattHours extends EnergyUnit {
   val conversionFactor = Watts.conversionFactor * MetricSystem.Kilo
   val symbol = "kWh"
@@ -241,6 +247,8 @@ object ExaElectronVolt extends EnergyUnit {
 object EnergyConversions {
   lazy val wattHour = WattHours(1)
   lazy val Wh = wattHour
+  lazy val milliwattHour = MilliwattHours(1)
+  lazy val mWh = milliwattHour
   lazy val kilowattHour = KilowattHours(1)
   lazy val kWh = kilowattHour
   lazy val megawattHour = MegawattHours(1)
@@ -291,6 +299,7 @@ object EnergyConversions {
     def terajoules = Terajoules(n)
 
     def Wh = WattHours(n)
+    def mWh = MilliwattHours(n)
     def kWh = KilowattHours(n)
     def MWh = MegawattHours(n)
     def GWh = GigawattHours(n)

shared/src/test/scala/squants/energy/EnergySpec.scala

@@ -28,6 +28,7 @@ class EnergySpec extends FlatSpec with Matchers {
 
   it should "create values using UOM factories" in {
     WattHours(1).toWattHours should be(1)
+    MilliwattHours(1).toMilliwattHours should be(1)
     KilowattHours(1).toKilowattHours should be(1)
     MegawattHours(1).toMegawattHours should be(1)
     GigawattHours(1).toGigawattHours should be(1)
@@ -60,6 +61,7 @@ class EnergySpec extends FlatSpec with Matchers {
   it should "create values from properly formatted Strings" in {
     Energy("10.22 J").get should be(Joules(10.22))
     Energy("10.22 Wh").get should be(WattHours(10.22))
+    Energy("10.22 mWh").get should be(MilliwattHours(10.22))
     Energy("10.22 kWh").get should be(KilowattHours(10.22))
     Energy("10.22 MWh").get should be(MegawattHours(10.22))
     Energy("10.22 GWh").get should be(GigawattHours(10.22))
@@ -83,6 +85,7 @@ class EnergySpec extends FlatSpec with Matchers {
     val x = WattHours(1)
 
     x.toWattHours should be(1)
+    x.toMilliwattHours should be(1 / MetricSystem.Milli)
     x.toKilowattHours should be(1 / MetricSystem.Kilo)
     x.toMegawattHours should be(1 / MetricSystem.Mega)
     x.toGigawattHours should be(1 / MetricSystem.Giga)
@@ -115,6 +118,7 @@ class EnergySpec extends FlatSpec with Matchers {
 
   it should "return properly formatted strings for all supported Units of Measure" in {
     WattHours(1).toString(WattHours) should be("1.0 Wh")
+    MilliwattHours(1).toString(MilliwattHours) should be("1.0 mWh")
     KilowattHours(1).toString(KilowattHours) should be("1.0 kWh")
     MegawattHours(1).toString(MegawattHours) should be("1.0 MWh")
     GigawattHours(1).toString(GigawattHours) should be("1.0 GWh")
@@ -207,6 +211,8 @@ class EnergySpec extends FlatSpec with Matchers {
 
     wattHour should be(WattHours(1))
     Wh should be(WattHours(1))
+    milliwattHour should be(MilliwattHours(1))
+    mWh should be(MilliwattHours(1))
     kilowattHour should be(KilowattHours(1))
     kWh should be(KilowattHours(1))
     megawattHour should be(MegawattHours(1))
@@ -242,6 +248,7 @@ class EnergySpec extends FlatSpec with Matchers {
 
     val d = 10D
     d.Wh should be(WattHours(d))
+    d.mWh should be(MilliwattHours(d))
     d.kWh should be(KilowattHours(d))
     d.MWh should be(MegawattHours(d))
     d.GWh should be(GigawattHours(d))
@@ -280,6 +287,7 @@ class EnergySpec extends FlatSpec with Matchers {
 
     "10.22 J".toEnergy.get should be(Joules(10.22))
     "10.22 Wh".toEnergy.get should be(WattHours(10.22))
+    "10.22 mWh".toEnergy.get should be(MilliwattHours(10.22))
     "10.22 kWh".toEnergy.get should be(KilowattHours(10.22))
     "10.22 MWh".toEnergy.get should be(MegawattHours(10.22))
     "10.22 GWh".toEnergy.get should be(GigawattHours(10.22))