scalatest: Added EitherValues demo.

Author: Daniel Barclay

src/test/scala/com/us/dsb/explore/libs/scalatest/ScratchTest.scala

@@ -0,0 +1,49 @@
+package com.us.dsb.explore.libs.scalatest
+
+import org.scalatest.funspec.AnyFunSpec
+
+class ScratchTest extends AnyFunSpec  {
+
+  // https://www.scalatest.org/user_guide/using_matchers#expectedExceptions
+  // https://www.scalatest.org/user_guide/using_matchers#usingCustomMatchers
+  // https://www.scalatest.org/user_guide/using_matchers#logicalExpressions
+  // https://www.scalatest.org/user_guide/using_matchers#checkingThatCodeDoesNotCompile
+  // https://www.scalatest.org/user_guide/using_matchers#inspectorShorthands
+
+  it("EitherValues") {
+    val right: Either[String, Int] = Right(1)
+
+    /* Without EitherValues, left/right failure gets simple "Either.left.get on Right"
+       with test line number down a bit in stack (but still linked in IntelliJ):
+         Either.left.get on Right
+         java.util.NoSuchElementException: Either.left.get on Right
+           at scala.util.Either$LeftProjection.get(Either.scala:537)
+           at com.us.dsb.explore.libs.scalatest.ScratchTest.$anonfun$new$1(ScratchTest.scala:10)
+           at ...
+     */
+    //assert("123" == right.left.get)
+    assert(1 == right.right.get)
+
+    import org.scalatest.EitherValues._
+
+    /* With EitherValues, gets display of actual value and test line number up
+       top:
+
+         The Either on which left.value was invoked was not defined as a Left; it was Right(1).
+         ScalaTestFailureLocation: com.us.dsb.explore.libs.scalatest.ScratchTest at (ScratchTest.scala:22)
+         org.scalatest.exceptions.TestFailedException: ...
+
+     */
+    //assert("123" == right.left.value)
+  }
+
+  ignore("OptionValues") {
+  }
+  ignore("PartialFunctionValues") {
+  }
+  ignore("Inside? matchPattern?") {
+  }
+  ignore("loneElement") {
+  }
+
+}