Pass error/value to UnwrapException message

src/main/kotlin/com/mikebull94/result/Unwrap.kt

@@ -18,7 +18,7 @@ fun <V, E> Result<V, E>.unwrap(): V {
 infix fun <V, E> Result<V, E>.expect(message: String): V {
     return when (this) {
         is Ok -> value
-        is Error -> throw UnwrapException(message)
+        is Error -> throw UnwrapException("$message $error")
     }
 }
 
@@ -37,7 +37,7 @@ fun <V, E> Result<V, E>.unwrapError(): E {
  */
 infix fun <V, E> Result<V, E>.expectError(message: String): E {
     return when (this) {
-        is Ok -> throw UnwrapException(message)
+        is Ok -> throw UnwrapException("$message $value")
         is Error -> error
     }
 }

src/test/kotlin/com/mikebull94/result/UnwrapTest.kt

@@ -14,29 +14,35 @@ internal class UnwrapTest {
 
     @Test
     internal fun `unwrap should throw an UnwrapException if not ok`() {
-        assertThrows(UnwrapException::class.java, {
+        val throwable = assertThrows(UnwrapException::class.java, {
             err(5000).unwrap()
-        }, "called Result.wrap on an Error value 5000")
+        })
+
+        assertThat(throwable.message, equalTo("called Result.wrap on an Error value 5000"))
     }
 
     @Test
     internal fun `expect should return the result value if ok`() {
-        val value = ok(1994).expect("the year should be 1994")
+        val value = ok(1994).expect("the year should be")
         assertThat(value, equalTo(1994))
     }
 
     @Test
     internal fun `expect should throw an UnwrapException with a specified message if not ok`() {
-        assertThrows(UnwrapException::class.java, {
+        val throwable = assertThrows(UnwrapException::class.java, {
-            err(1994).expect("the year should be 1994")
+            err(1994).expect("the year should be")
-        }, "the year should be 1994")
+        })
+
+        assertThat(throwable.message, equalTo("the year should be 1994"))
     }
 
     @Test
     internal fun `unwrapError should throw an UnwrapException if ok`() {
-        assertThrows(UnwrapException::class.java, {
+        val throwable = assertThrows(UnwrapException::class.java, {
             ok("example").unwrapError()
-        }, "called Result.unwrapError on an Ok value example")
+        })
+
+        assertThat(throwable.message, equalTo("called Result.unwrapError on an Ok value example"))
     }
 
     @Test
@@ -47,14 +53,16 @@ internal class UnwrapTest {
 
     @Test
     internal fun `expectError should throw an UnwrapException with a specified message if ok`() {
-        assertThrows(UnwrapException::class.java, {
+        val throwable = assertThrows(UnwrapException::class.java, {
-            ok(2010).expectError("the year should be 2010")
+            ok(2010).expectError("the year should be")
-        }, "the year should be 2010")
+        })
+
+        assertThat(throwable.message, equalTo("the year should be 2010"))
     }
 
     @Test
     internal fun `expectError should return the result error if not ok`() {
-        val error = err(2010).expectError("the year should be 2010")
+        val error = err(2010).expectError("the year should be")
         assertThat(error, equalTo(2010))
     }
 }