Display hours of play time only if game lasts more than one hour

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Move the popup messages of the main screen to the absolute bottom of the screen, now covering the
  bottom app bar. Avoids covering the bottom row of number buttons when checking if there are errors.
 - Mark 'Fast Finishing Mode' as stable.
+- Show hours of play time only if the game lasts longer than one hour.
 
 ### Deprecated
 

gauguin-core/src/main/kotlin/org/piepmeyer/gauguin/Utils.kt

@@ -5,7 +5,11 @@ import kotlin.time.Duration
 object Utils {
     fun displayableGameDuration(gameDuration: Duration): String {
         return gameDuration.toComponents { hours, minutes, seconds, _ ->
-            String.format("%02d:%02d:%02d", hours, minutes, seconds)
+            if (hours == 0L) {
+                String.format("%02d:%02d", minutes, seconds)
+            } else {
+                String.format("%d:%02d:%02d", hours, minutes, seconds)
+            }
         }
     }
 }

gauguin-core/src/test/kotlin/org/piepmeyer/gauguin/UtilsTest.kt

@@ -0,0 +1,30 @@
+package org.piepmeyer.gauguin
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+import kotlin.time.Duration.Companion.hours
+import kotlin.time.Duration.Companion.minutes
+import kotlin.time.Duration.Companion.seconds
+
+class UtilsTest : FunSpec({
+
+    test("duration of zero shows minutes and seconds") {
+        Utils.displayableGameDuration(0.minutes) shouldBe "00:00"
+    }
+
+    test("duration of 61 seconds shows 1:01") {
+        Utils.displayableGameDuration(61.seconds) shouldBe "01:01"
+    }
+
+    test("duration less than one hour does not contain hour component") {
+        Utils.displayableGameDuration(50.minutes) shouldBe "50:00"
+    }
+
+    test("duration with more than one hour does contain hour component") {
+        Utils.displayableGameDuration(90.minutes) shouldBe "1:30:00"
+    }
+
+    test("duration with two-digit hours does contain two-digit hour component") {
+        Utils.displayableGameDuration(23.hours) shouldBe "23:00:00"
+    }
+})