Add similarity to haveValues and haveValue (#48)

kotest-assertions/kotest-assertions-core/src/commonMain/kotlin/io/kotest/matchers/maps/MapMatchers.kt

@@ -29,23 +29,51 @@ fun <K> haveKeys(vararg keys: K): Matcher<Map<K, Any?>> = object : Matcher<Map<K
 }
 
 fun <V> haveValue(v: V): Matcher<Map<*, V>> = object : Matcher<Map<*, V>> {
-   override fun test(value: Map<*, V>) = MatcherResult(
-      value.containsValue(v),
-      { "Map should contain value $v" },
-      { "Map should not contain value $v" })
+   override fun test(value: Map<*, V>): MatcherResult {
+      val passed = value.containsValue(v)
+      val possibleMatchesDescription = possibleMatchesForMissingElements(
+         setOf(v),
+         value.values.toSet(),
+         "value"
+      )
+      return MatcherResult(
+         passed,
+         { "Map should contain value $v$possibleMatchesDescription" },
+         { "Map should not contain value $v" })
+   }
 }
 
 fun <V> haveValues(vararg values: V): Matcher<Map<*, V>> = object : Matcher<Map<*, V>> {
    override fun test(value: Map<*, V>): MatcherResult {
       val valuesNotPresentInMap = values.filterNot { value.containsValue(it) }
+      val possibleMatchesDescription = possibleMatchesForMissingElements(
+         valuesNotPresentInMap.toSet(),
+         value.values.toSet(),
+         "values"
+      )
       return MatcherResult(
          valuesNotPresentInMap.isEmpty(),
-         { "Map did not contain the values ${values.joinToString(", ")}" },
+         { "Map did not contain the values ${valuesNotPresentInMap.joinToString(", ")}$possibleMatchesDescription" },
          { "Map should not contain the values ${values.joinToString(", ")}" }
       )
    }
 }
 
+internal fun <K> possibleMatchesForMissingElements(
+   unexpected: Set<K>,
+   expected: Set<K>,
+   elementTypeDescription: String
+): String {
+   val possibleMatches = unexpected.
+   map {
+      possibleMatchesDescription(expected, it)
+   }.filter {
+      it.isNotEmpty()
+   }.joinToString("\n")
+   return if (possibleMatches.isEmpty()) ""
+   else "\nPossible matches for missing $elementTypeDescription:\n$possibleMatches"
+}
+
 fun <K> containAnyKeys(vararg keys: K): Matcher<Map<K, Any?>> = object : Matcher<Map<K, Any?>> {
    override fun test(value: Map<K, Any?>): MatcherResult {
       val passed = keys.any { value.containsKey(it) }

kotest-assertions/kotest-assertions-core/src/jvmTest/kotlin/com/sksamuel/kotest/matchers/maps/MapMatchersTest.kt

@@ -55,6 +55,23 @@ class MapMatchersTest : WordSpec() {
                map.shouldContainValue("c")
             }.message.shouldBe("Map should contain value c")
          }
+         "find similarities for values not found" {
+            shouldThrow<AssertionError> {
+               mapOf(
+                  1 to sweetGreenApple,
+                  2 to sweetRedApple,
+                  3 to sourYellowLemon
+               ).shouldContainValue(sweetGreenPear)
+            }.message.shouldBe("""
+            |Map should contain value Fruit(name=pear, color=green, taste=sweet)
+            |Possible matches for missing value:
+            |
+            | expected: Fruit(name=apple, color=green, taste=sweet),
+            |  but was: Fruit(name=pear, color=green, taste=sweet),
+            |  The following fields did not match:
+            |    "name" expected: <"apple">, but was: <"pear">
+            """.trimMargin())
+         }
       }
 
       "contain" should {
@@ -116,6 +133,24 @@ class MapMatchersTest : WordSpec() {
                map.shouldNotContainValues("a", "b")
             }.message.shouldBe("Map should not contain the values a, b")
          }
+
+         "find similarities for values not found" {
+            shouldThrow<AssertionError> {
+               mapOf(
+                  1 to sweetGreenApple,
+                  2 to sweetRedApple,
+                  3 to sourYellowLemon
+               ).shouldContainValues(sweetGreenApple, sweetGreenPear)
+            }.message.shouldBe("""
+            |Map did not contain the values Fruit(name=pear, color=green, taste=sweet)
+            |Possible matches for missing values:
+            |
+            | expected: Fruit(name=apple, color=green, taste=sweet),
+            |  but was: Fruit(name=pear, color=green, taste=sweet),
+            |  The following fields did not match:
+            |    "name" expected: <"apple">, but was: <"pear">
+            """.trimMargin())
+         }
       }
 
       "containAnyKeys" should {