Describe a repeated minute in a routine's schedule once

CHANGELOG.md

@@ -57,6 +57,12 @@ on a still screen, for an action that never happened.
   three — but the Bot was still offered the tools, so it reached for one, was refused, and spent the
   turn saying so. The tools a switch turns off are now withheld from the Bot in the first place.
 
+### A repeated minute in a routine's schedule is described once
+
+A schedule like `0,30,0 9 * * *` fires at 09:00 and 09:30, but the routines page and the model were
+told "Every day at 09:00, 09:00 and 09:30". Repeated minutes are now said once, as repeated weekdays
+already were.
+
 ### An app you have not connected is offered where you are reading
 
 A Bot asked to use an app whose account the person had not connected answered with the name of a

server/src/routines/schedule.ts

@@ -298,7 +298,9 @@ export function describeCron(cron: string): string {
         .split(",")
         .map((part) => parsePlainInt(part, 0, 59));
       if (minutes.every((value): value is number => value !== null)) {
-        const times = [...minutes]
+        // De-duplicated like `weekdays`: cron fires once for `0,0`, so it must not read as
+        // "09:00 and 09:00".
+        const times = [...new Set(minutes)]
           .sort((a, b) => a - b)
           .map((value) => `${pad2(hour)}:${pad2(value)}`);
         return `Every day at ${joinWords(times)}`;

server/tests/routine-schedule.test.ts

@@ -182,6 +182,12 @@ describe("describeCron", () => {
     expect(describeCron("0,30 9 * * *")).toBe("Every day at 09:00 and 09:30");
   });
 
+  // cron fires once per distinct minute, so a repeated minute must not be described twice.
+  test("a repeated minute in the list is described once", () => {
+    expect(describeCron("0,30,0 9 * * *")).toBe("Every day at 09:00 and 09:30");
+    expect(describeCron("15,15 9 * * *")).toBe("Every day at 09:15");
+  });
+
   test("falls through to the raw expression when it is stranger than words", () => {
     expect(describeCron("*/7 3,4 * * *")).toBe("*/7 3,4 * * *");
   });