allow environment variable overrides for configuration. (#13)

* allow environment variable overrides for configuration. avoid using deprecated scalatest traits

* additional doc

src/main/scala/com/workday/warp/common/PropertyEntry.scala

@@ -7,6 +7,9 @@ package com.workday.warp.common
   */
 case class PropertyEntry(propertyName: String, isRequired: Boolean, defaultValue: String) {
 
+  // used as a name for looking up a corresponding environment variable
+  val envVarName: String = this.propertyName.map(_.toUpper).replace(".", "_")
+
   def this(propertyName: String, isRequired: Boolean) = this(propertyName, isRequired, None.orNull)
   def this(propertyName: String) = this(propertyName, isRequired = false)
 

src/main/scala/com/workday/warp/common/WarpPropertyManager.scala

@@ -174,15 +174,16 @@ object WarpPropertyManager {
 
 
   /**
-   * Computes a map containing the assigned values of each WarpProperty according to the following sources in order of
-   * decreasing precedence:
-   *
-   *   1: jvm system properties
-   *   2: properties from the warp configuration file (warp.properties)
-   *   3: default property values provided in the enum
-   *
-   * @return an immutable Map containing the values for each WarpProperty
-   */
+    * Computes a map containing the assigned values of each WarpProperty according to the following sources in order of
+    * decreasing precedence:
+    *
+    *   1: environment variables
+    *   2: jvm system properties
+    *   3: properties from the warp configuration file (warp.properties)
+    *   4: default property values provided in the enum
+    *
+    * @return an immutable [[Map]] containing the values for each WarpProperty
+    */
   def overlayProperties: Map[String, String] = {
     val properties: mutable.Map[String, String] = mutable.Map[String, String]()
 
@@ -206,6 +207,11 @@ object WarpPropertyManager {
       this.systemProps.get(key) foreach { value =>
         properties += (key -> value)
       }
+
+      // if we find an environment variable override, add it to our map
+      sys.env.get(entry.envVarName) foreach { value =>
+        properties += (key -> value)
+      }
     }
 
     properties.toMap

src/main/scala/com/workday/warp/common/spec/WarpJUnitSpec.scala

@@ -3,7 +3,7 @@ package com.workday.warp.common.spec
 import com.workday.telemetron.spec.HasTelemetron
 import com.workday.warp.common.utils.TryMatchers
 import org.scalatest._
-import org.scalatest.junit.{AssertionsForJUnit, JUnitSuite}
+import org.scalatestplus.junit.{AssertionsForJUnit, JUnitSuite}
 
 /**
   * Base class for WARP framework tests written in scalatest.

src/test/scala/com/workday/telemetron/junit/SurroundOnceSpec.scala

@@ -3,7 +3,7 @@ package com.workday.telemetron.junit
 import com.workday.telemetron.annotation.{AfterOnce, BeforeOnce, Schedule}
 import org.junit.{Rule, Test}
 import org.scalatest.Matchers
-import org.scalatest.junit.JUnitSuite
+import org.scalatestplus.junit.JUnitSuite
 
 /**
   * Created by vignesh.kalidas on 2/8/17.

src/test/scala/com/workday/warp/common/PropertyEntrySpec.scala

@@ -15,5 +15,6 @@ class PropertyEntrySpec extends WarpJUnitSpec {
   def constructor(): Unit = {
     new PropertyEntry("com.workday.warp.foo").propertyName should be ("com.workday.warp.foo")
     PropertyEntry("com.workday.warp.foo").propertyName should be ("com.workday.warp.foo")
+    PropertyEntry("com.workday.warp.foo").envVarName should be ("COM_WORKDAY_WARP_FOO")
   }
 }