Test to check multiple contexts work

src/context.zig

@@ -157,3 +157,33 @@ pub fn Context(comptime ctx: anytype) type {
         }
     };
 }
+
+test "Context multiple contexts" {
+    const flecszigble = @import("./main.zig");
+    const expect = @import("./test/expect.zig");
+
+    flecszigble.init(std.testing.allocator);
+    var world1 = try Context(1).World.initMinimal();
+    var world2 = try Context(2).World.initMinimal();
+    defer world1.deinit();
+    defer world2.deinit();
+
+    const Foo = struct {};
+    const Bar = struct {};
+
+    const foo1 = try world1.tag(Foo);
+    const bar1 = try world1.tag(Bar);
+    // Register tags in opposite order in `world2`.
+    const bar2 = try world2.tag(Bar);
+    const foo2 = try world2.tag(Foo);
+
+    try expect.equal(foo1, try world1.lookupType(Foo));
+    try expect.equal(bar1, try world1.lookupType(Bar));
+    try expect.equal(foo2, try world2.lookupType(Foo));
+    try expect.equal(bar2, try world2.lookupType(Bar));
+
+    // Due to registration order, and IDs being unique to each World,
+    // `Foo` from `world1` should have the same ID as `Bar` from `world2`.
+    try expect.equal(foo1.raw, bar2.raw);
+    try expect.equal(bar1.raw, foo2.raw);
+}