diff --git a/build.zig b/build.zig
index 62da26c53c..8cc70f2c7a 100644
--- a/build.zig
+++ b/build.zig
@@ -764,6 +764,7 @@ const MiniCiStep = struct {
         // Run the sequence of `zig build` commands that make up the
         // mini CI pipeline.
         try runSubBuild(step, "fmt", "zig build fmt");
+        try checkTestWiring(step);
         try runSubBuild(step, null, "zig build");
         try checkBuiltinRocFormatting(step);
         try runSubBuild(step, "snapshot", "zig build snapshot");
@@ -882,6 +883,39 @@ const MiniCiStep = struct {
             },
         }
     }
+
+    fn checkTestWiring(step: *Step) !void {
+        const b = step.owner;
+        std.debug.print("---- minici: checking test wiring ----\n", .{});
+
+        var child_argv = std.ArrayList([]const u8).empty;
+        defer child_argv.deinit(b.allocator);
+
+        try child_argv.append(b.allocator, b.graph.zig_exe);
+        try child_argv.append(b.allocator, "run");
+        try child_argv.append(b.allocator, "ci/check_test_wiring.zig");
+
+        var child = std.process.Child.init(child_argv.items, b.allocator);
+        child.stdin_behavior = .Inherit;
+        child.stdout_behavior = .Inherit;
+        child.stderr_behavior = .Inherit;
+
+        const term = try child.spawnAndWait();
+
+        switch (term) {
+            .Exited => |code| {
+                if (code != 0) {
+                    return step.fail(
+                        "Test wiring check failed. Run 'zig run ci/check_test_wiring.zig' to see details.",
+                        .{},
+                    );
+                }
+            },
+            else => {
+                return step.fail("zig run ci/check_test_wiring.zig terminated abnormally", .{});
+            },
+        }
+    }
 };
 
 fn createAndRunBuiltinCompiler(
diff --git a/src/check/mod.zig b/src/check/mod.zig
index 100817cccc..186ebf0c34 100644
--- a/src/check/mod.zig
+++ b/src/check/mod.zig
@@ -41,4 +41,5 @@ test "check tests" {
     std.testing.refAllDecls(@import("test/builtin_scope_test.zig"));
     std.testing.refAllDecls(@import("test/num_type_inference_test.zig"));
     std.testing.refAllDecls(@import("test/unify_test.zig"));
+    std.testing.refAllDecls(@import("test/instantiate_tag_union_test.zig"));
 }