From 447051631a22d286ff897504cb0f0102ea86f8c8 Mon Sep 17 00:00:00 2001
From: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>
Date: Mon, 25 Mar 2024 11:24:48 +0100
Subject: [PATCH] Add context to the DayOfWeek constructor precondition (#371)

---
 core/common/src/DayOfWeek.kt      |  2 +-
 core/common/test/DayOfWeekTest.kt | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 core/common/test/DayOfWeekTest.kt

diff --git a/core/common/src/DayOfWeek.kt b/core/common/src/DayOfWeek.kt
index 54013d40..496d61be 100644
--- a/core/common/src/DayOfWeek.kt
+++ b/core/common/src/DayOfWeek.kt
@@ -27,6 +27,6 @@ public val DayOfWeek.isoDayNumber: Int get() = ordinal + 1
  * Returns the [DayOfWeek] instance for the given ISO-8601 week day number. Monday is 1, Sunday is 7.
  */
 public fun DayOfWeek(isoDayNumber: Int): DayOfWeek {
-    require(isoDayNumber in 1..7)
+    require(isoDayNumber in 1..7) { "Expected ISO day-of-week number in 1..7, got $isoDayNumber" }
     return DayOfWeek.entries[isoDayNumber - 1]
 }
diff --git a/core/common/test/DayOfWeekTest.kt b/core/common/test/DayOfWeekTest.kt
new file mode 100644
index 00000000..cbdb252a
--- /dev/null
+++ b/core/common/test/DayOfWeekTest.kt
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.datetime.test
+
+import kotlinx.datetime.*
+import kotlin.test.*
+
+class DayOfWeekTest {
+
+    @Test
+    fun testDayOfWeek() {
+        for (i in 1..7) {
+            assertEquals(i, DayOfWeek(i).isoDayNumber)
+        }
+        assertFailsWith<IllegalArgumentException> { DayOfWeek(-1) }
+        assertFailsWith<IllegalArgumentException> { DayOfWeek(8) }
+        assertFailsWith<IllegalArgumentException> { DayOfWeek(Int.MIN_VALUE) }
+    }
+}
\ No newline at end of file