Ensure mission exists before inserting mission launch entity

src/MissionControl.Server/Endpoints/Missions/MissionLaunches/CreateMissionLaunch.cs

@@ -1,5 +1,6 @@
 using FastEndpoints;
 using FluentValidation;
+using Microsoft.EntityFrameworkCore;
 using MissionControl.Data;
 using MissionControl.Domain.Entities;
 
@@ -15,6 +16,13 @@ public class CreateMissionLaunch(MissionControlContext dbContext)
 
     public override async Task HandleAsync(CreateMissionLaunchRequest req, CancellationToken ct)
     {
+        var missionExists = await dbContext.Missions.AnyAsync(mission => mission.Id == req.MissionId, ct);
+        if (!missionExists)
+        {
+            await Send.NotFoundAsync(ct);
+            return;
+        }
+
         var missionLaunch = new MissionLaunch
         {
             ScheduledFor = req.ScheduledFor,

test/MissionControl.Server.Tests/Endpoints/Missions/MissionLaunches/CreateMissionLaunchTests.cs

@@ -0,0 +1,30 @@
+using FastEndpoints;
+using Microsoft.AspNetCore.Http;
+using Microsoft.EntityFrameworkCore;
+using MissionControl.Domain.Entities;
+using MissionControl.Server.Endpoints.Missions.MissionLaunches;
+using Shouldly;
+
+namespace MissionControl.Server.Tests.Endpoints.Missions.MissionLaunches;
+
+public class CreateMissionLaunchTests
+{
+    [Fact]
+    public async Task Returns_not_found_when_requested_mission_does_not_exist()
+    {
+        using var database = new TestDatabase();
+        var endpoint = Factory.Create<CreateMissionLaunch>(database.Context);
+        var request = new CreateMissionLaunchRequest
+        {
+            MissionId = Guid.NewGuid(),
+            ScheduledFor = DateTimeOffset.UtcNow,
+            Status = "Pending",
+        };
+
+        await endpoint.HandleAsync(request, CancellationToken.None);
+
+        endpoint.HttpContext.Response.StatusCode.ShouldBe(StatusCodes.Status404NotFound);
+
+        (await database.Context.MissionLaunches.AnyAsync()).ShouldBeFalse();
+    }
+}