diff --git a/exp_roles/package.json b/exp_roles/package.json
index 1e462135..05f53e71 100644
--- a/exp_roles/package.json
+++ b/exp_roles/package.json
@@ -8,7 +8,8 @@
 	"main": "dist/node/index.js",
 	"scripts": {
 		"prepare": "tsc --build && webpack-cli --env production",
-		"test": "tap --disable-coverage --allow-empty-coverage test/*.test.js"
+		"test": "tap --disable-coverage --allow-empty-coverage test/*.test.js",
+		"coverage": "tap --coverage-report=text test/*.test.js"
 	},
 	"engines": {
 		"node": ">=18"
diff --git a/exp_roles/test/controller.test.js b/exp_roles/test/controller.test.js
index 8b47e5cb..bf2f843c 100644
--- a/exp_roles/test/controller.test.js
+++ b/exp_roles/test/controller.test.js
@@ -20,6 +20,12 @@ lib.Link.register(messages.AssignmentUpdateRequest);
 
 const logger = { child: () => logger, info: () => {}, warn: () => {}, error: () => {}, verbose: () => {} };
 
+// Silence the singleton logger to avoid polluting the test output
+lib.logger.silent = true;
+t.after(() => {
+	lib.logger.silent = false;
+});
+
 /** Build a plugin around a real controller, which is side effect free while not started. */
 async function startPlugin(t2, { roles = [] } = {}) {
 	const controllerConfig = new lib.ControllerConfig("controller", {
@@ -173,6 +179,18 @@ t.test("class ControllerPlugin", t2 => {
 		t3.strictSame(applied.length, 1, "other player events do not");
 	});
 
+	t2.test(".handleRoleListRequest() returns the current roles", async t3 => {
+		const { plugin } = await startPlugin(t3, {
+			roles: [role(1, "Player"), role(5, "Moderator")],
+		});
+		plugin.roleMeta.set(new messages.RoleMetaRecord(5, 2, 0, "Mod"));
+
+		const response = await plugin.handleRoleListRequest(new messages.RoleListRequest());
+		t3.strictSame(response.length, 2, "the current roles are returned");
+		t3.ok(response.some(record => record.name === "Moderator"));
+		t3.ok(response.some(record => record.name === "Player"));
+	});
+
 	t2.test(".handleRoleMetaUpdateRequest() validates the role", async t3 => {
 		const { plugin } = await startPlugin(t3, { roles: [role(1, "Player"), role(5, "Moderator")] });
 
@@ -187,6 +205,19 @@ t.test("class ControllerPlugin", t2 => {
 		t3.strictSame(plugin.roleMeta.get(5).shortHand, "Mod", "the properties are stored");
 	});
 
+	t2.test(".handleAssignmentListRequest() returns the current assignments", async t3 => {
+		const { plugin, controller } = await startPlugin(t3, {
+			roles: [role(1, "Player"), role(5, "Moderator")],
+		});
+		controller.users.createUser("alice").set("roleIds", new Set([5]));
+		controller.users.createUser("bob");
+
+		const response = await plugin.handleAssignmentListRequest(new messages.AssignmentListRequest());
+		t3.strictSame(response.length, 1, "the current assignments are returned");
+		t3.strictSame(response[0].name, "alice");
+		t3.strictSame(response[0].roleIds, new Set([5]), "the default role is not listed");
+	});
+
 	t2.test(".handleAssignmentSubscription() replays only newer records", async t3 => {
 		const { plugin, controller } = await startPlugin(t3, { roles: [role(1, "Player"), role(5, "Moderator")] });
 		controller.users.createUser("alice").set("roleIds", new Set([5]));
diff --git a/exp_roles/test/messages.test.js b/exp_roles/test/messages.test.js
index ba89b550..8ec26550 100644
--- a/exp_roles/test/messages.test.js
+++ b/exp_roles/test/messages.test.js
@@ -7,18 +7,18 @@ const fullMeta = new messages.RoleMetaRecord(
 	7, 3, 1, "Mod", "[Mod]", new messages.RoleColor(1, 2, 3), 3600000, true, 12345, false,
 );
 
-t.test("class RoleColor", subtest => {
-	testRoundTripJsonSerialisable(messages.RoleColor, testMatrix(
+t.test("class RoleColor", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.RoleColor, testMatrix(
 		[0, 255], // r
 		[0, 128], // g
 		[0, 1], // b
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class RoleMetaRecord", subtest => {
-	testRoundTripJsonSerialisable(messages.RoleMetaRecord, testMatrix(
+t.test("class RoleMetaRecord", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.RoleMetaRecord, testMatrix(
 		[7], // id
 		[3], // order
 		[0, 1], // priority
@@ -30,12 +30,12 @@ t.test("class RoleMetaRecord", subtest => {
 		[0, 12345], // updatedAtMs
 		[false, true], // isDeleted
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class RoleRecord", subtest => {
-	testRoundTripJsonSerialisable(messages.RoleRecord, testMatrix(
+t.test("class RoleRecord", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.RoleRecord, testMatrix(
 		[7], // id
 		["Moderator"], // name
 		[[], ["a.b", "c.d"]], // permissions
@@ -44,67 +44,73 @@ t.test("class RoleRecord", subtest => {
 		[0, 12345], // updatedAtMs
 		[false, true], // isDeleted
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class AssignmentRecord", subtest => {
-	testRoundTripJsonSerialisable(messages.AssignmentRecord, testMatrix(
+t.test("class AssignmentRecord", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.AssignmentRecord, testMatrix(
 		["alice"], // name
 		[new Set(), new Set([5, 6])], // roleIds
 		[0, 12345], // updatedAtMs
 		[false, true], // isDeleted
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.test("get id()", t3 => {
+		const record = new messages.AssignmentRecord("alice", new Set([5]), 12345);
+		t3.equal(record.id, "alice");
+		t3.end();
+	});
+
+	t2.end();
 });
 
 const sampleRecord = new messages.RoleRecord(7, "Moderator", ["a.b"], fullMeta, true, 12345);
 const sampleAssignment = new messages.AssignmentRecord("alice", new Set([5]), 12345);
 
-t.test("class RoleUpdatedEvent", subtest => {
-	testRoundTripJsonSerialisable(messages.RoleUpdatedEvent, testMatrix(
+t.test("class RoleUpdatedEvent", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.RoleUpdatedEvent, testMatrix(
 		[[], [sampleRecord]], // updates
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class AssignmentUpdatedEvent", subtest => {
-	testRoundTripJsonSerialisable(messages.AssignmentUpdatedEvent, testMatrix(
+t.test("class AssignmentUpdatedEvent", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.AssignmentUpdatedEvent, testMatrix(
 		[[], [sampleAssignment]], // updates
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class RoleMetaUpdateRequest", subtest => {
-	testRoundTripJsonSerialisable(messages.RoleMetaUpdateRequest, testMatrix(
+t.test("class RoleMetaUpdateRequest", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.RoleMetaUpdateRequest, testMatrix(
 		[new messages.RoleMetaRecord(7, 3), fullMeta], // meta
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("class AssignmentUpdateRequest", subtest => {
-	testRoundTripJsonSerialisable(messages.AssignmentUpdateRequest, testMatrix(
+t.test("class AssignmentUpdateRequest", t2 => {
+	testRoundTripJsonSerialisable(t2, messages.AssignmentUpdateRequest, testMatrix(
 		["alice"], // name
 		[[], [5]], // assign
 		[[], [6]], // unassign
 	));
-	subtest.pass("round trips");
-	subtest.end();
+
+	t2.end();
 });
 
-t.test("encodeRolesForLua() sends each permission name once", subtest => {
+t.test("encodeRolesForLua() sends each permission name once", t2 => {
 	const meta = id => new messages.RoleMetaRecord(id, id);
 	const encoded = messages.encodeRolesForLua([
 		new messages.RoleRecord(1, "A", ["p.one", "p.two"], meta(1)),
 		new messages.RoleRecord(2, "B", ["p.two", "p.three"], meta(2)),
 	]);
 
-	subtest.strictSame(encoded.permission_names, ["p.one", "p.two", "p.three"], "names are deduplicated");
-	subtest.strictSame(encoded.roles[0].permissions, [0, 1], "indexes are zero based");
-	subtest.strictSame(encoded.roles[1].permissions, [1, 2], "shared names reuse their index");
-	subtest.end();
+	t2.strictSame(encoded.permission_names, ["p.one", "p.two", "p.three"], "names are deduplicated");
+	t2.strictSame(encoded.roles[0].permissions, [0, 1], "indexes are zero based");
+	t2.strictSame(encoded.roles[1].permissions, [1, 2], "shared names reuse their index");
+	t2.end();
 });
diff --git a/exp_roles/test/control.test.js b/exp_roles/test/module.test.js
similarity index 62%
rename from exp_roles/test/control.test.js
rename to exp_roles/test/module.test.js
index 70272979..2e5d4aa5 100644
--- a/exp_roles/test/control.test.js
+++ b/exp_roles/test/module.test.js
@@ -3,12 +3,12 @@ const path = require("node:path");
 const t = require("tap");
 const { reportLuaTests } = require("../../test/lua/runner");
 
-const envFile = path.join(__dirname, "lua", "env.lua");
+const envFile = path.join(__dirname, "module", "env.lua");
 
 // Each file runs in its own lua state, and each test in a fresh environment
-t.test("module/control.lua", t2 => {
+t.test("control.lua", t2 => {
 	for (const file of ["lookup.lua", "players.lua", "assignment.lua", "sync.lua", "holders.lua"]) {
-		t2.test(`lua/${file}`, subtest => reportLuaTests(subtest, envFile, path.join(__dirname, "lua", file)));
+		t2.test(file, t3 => reportLuaTests(t3, envFile, path.join(__dirname, "module", file)));
 	}
 	t2.end();
 });
diff --git a/exp_roles/test/lua/assignment.lua b/exp_roles/test/module/assignment.lua
similarity index 98%
rename from exp_roles/test/lua/assignment.lua
rename to exp_roles/test/module/assignment.lua
index 9a99dd58..a774af5f 100644
--- a/exp_roles/test/lua/assignment.lua
+++ b/exp_roles/test/module/assignment.lua
@@ -1,5 +1,5 @@
 --- Tests for the assignment methods of module/control.lua
-local Suite = ... --- The suite this file adds its tests to, see test/lua/framework.lua
+local Suite = ... --- @type Suite The suite this file adds its tests to, see env.lua
 local test, check, eq, empty = Suite.test, Suite.check, Suite.eq, Suite.empty
 
 --- alice is a moderator and bob a regular, with changes sent to the controller
diff --git a/exp_roles/test/lua/env.lua b/exp_roles/test/module/env.lua
similarity index 94%
rename from exp_roles/test/lua/env.lua
rename to exp_roles/test/module/env.lua
index b1c7f908..5b612329 100644
--- a/exp_roles/test/lua/env.lua
+++ b/exp_roles/test/module/env.lua
@@ -8,10 +8,10 @@ returned here becomes `...` in each test file.
 ]]
 
 local shared_root = ... --- @type string
-local source = assert(debug.getinfo(1, "S")).source
-local plugin_root = assert(source:match("^@(.*)/test/lua/env%.lua$"))
+local source = assert(debug.getinfo(1, "S")).source:gsub("\\", "/")
+local plugin_root = assert(source:match("^@(.*)/test/module/env%.lua$"))
 
-local Framework = assert(loadfile(shared_root .. "/framework.lua"))()
+local Framework = assert(loadfile(shared_root .. "/framework.lua"))() --- @type Framework
 
 --- Standard fixture: permission names sent once and referenced by zero based index
 local permission_names = {
@@ -48,7 +48,7 @@ for _, record in ipairs(role_records()) do
 end
 
 return Framework.suite(function(env)
-    env.Roles = assert(loadfile(plugin_root .. "/module/control.lua"))()
+    env.Roles = assert(loadfile(plugin_root .. "/module/control.lua"))() --- @type ExpRoles
     env.Roles.on_server_startup()
 
     --- Get a fixture role by name, failing the test when it does not exist
diff --git a/exp_roles/test/lua/holders.lua b/exp_roles/test/module/holders.lua
similarity index 96%
rename from exp_roles/test/lua/holders.lua
rename to exp_roles/test/module/holders.lua
index 8ee4c91f..6d5cdb16 100644
--- a/exp_roles/test/lua/holders.lua
+++ b/exp_roles/test/module/holders.lua
@@ -1,5 +1,5 @@
 --- Tests for listing and printing to the players who hold a role
-local Suite = ... --- The suite this file adds its tests to, see test/lua/framework.lua
+local Suite = ... --- @type Suite The suite this file adds its tests to, see test/lua/framework.lua
 local test, check, eq = Suite.test, Suite.check, Suite.eq
 
 --- alice and dave are moderators with dave offline, zed has never joined
diff --git a/exp_roles/test/lua/lookup.lua b/exp_roles/test/module/lookup.lua
similarity index 97%
rename from exp_roles/test/lua/lookup.lua
rename to exp_roles/test/module/lookup.lua
index 2479e6c8..e203fbc6 100644
--- a/exp_roles/test/lua/lookup.lua
+++ b/exp_roles/test/module/lookup.lua
@@ -1,5 +1,5 @@
 --- Tests for the role lookup functions of module/control.lua
-local Suite = ... --- The suite this file adds its tests to, see test/lua/framework.lua
+local Suite = ... --- @type Suite The suite this file adds its tests to, see test/lua/framework.lua
 local test, check, eq = Suite.test, Suite.check, Suite.eq
 
 test("get_role() returns the role with the given clusterio id", function(env)
diff --git a/exp_roles/test/lua/players.lua b/exp_roles/test/module/players.lua
similarity index 97%
rename from exp_roles/test/lua/players.lua
rename to exp_roles/test/module/players.lua
index a13dce6c..50513a30 100644
--- a/exp_roles/test/lua/players.lua
+++ b/exp_roles/test/module/players.lua
@@ -1,5 +1,5 @@
 --- Tests for the player checks of module/control.lua
-local Suite = ... --- The suite this file adds its tests to, see test/lua/framework.lua
+local Suite = ... --- @type Suite The suite this file adds its tests to, see test/lua/framework.lua
 local test, check, eq = Suite.test, Suite.check, Suite.eq
 
 --- alice is a moderator, bob is a regular, and carol has only the default role
diff --git a/exp_roles/test/lua/sync.lua b/exp_roles/test/module/sync.lua
similarity index 98%
rename from exp_roles/test/lua/sync.lua
rename to exp_roles/test/module/sync.lua
index 2a94875d..64daf581 100644
--- a/exp_roles/test/lua/sync.lua
+++ b/exp_roles/test/module/sync.lua
@@ -1,5 +1,5 @@
 --- Tests for the sync entry points of module/control.lua
-local Suite = ... --- The suite this file adds its tests to, see test/lua/framework.lua
+local Suite = ... --- @type Suite The suite this file adds its tests to, see test/lua/framework.lua
 local test, check, eq, empty = Suite.test, Suite.check, Suite.eq, Suite.empty
 
 --- alice is a moderator and carol has only the default role, both connected
diff --git a/exp_roles/test/seed.test.js b/exp_roles/test/seed.test.js
index 010dbd5d..adcb0987 100644
--- a/exp_roles/test/seed.test.js
+++ b/exp_roles/test/seed.test.js
@@ -6,35 +6,57 @@ const { seedRoles, flattenSeedPermissions } = require("../dist/node/seed");
 // Importing this defines the exp_scenario permissions the seed grants
 require("@expcluster/scenario/dist/node/permissions");
 
-t.test("seedRoles grant only defined permissions", subtest => {
+t.test("seedRoles[] grant only defined permissions", t2 => {
 	for (const role of seedRoles) {
-		for (const permission of flattenSeedPermissions(role)) {
-			subtest.ok(lib.permissions.has(permission), `${role.name} grants defined permission ${permission}`);
+		for (const permission of role.permissions) {
+			t2.ok(lib.permissions.has(permission), `${role.name} grants defined permission ${permission}`);
 		}
 	}
-	subtest.end();
+	t2.end();
 });
 
-t.test("flattenSeedPermissions() carries parents into their children", subtest => {
+t.test("seedRoles[] are unique with one default and one admin", t2 => {
+	const names = seedRoles.map(role => role.name);
+	t2.strictSame(names.length, new Set(names).size, "names are unique");
+	t2.strictSame(seedRoles.filter(role => role.isDefault).length, 1, "one default role");
+	t2.strictSame(seedRoles.filter(role => role.isAdmin).length, 1, "one admin role");
+	t2.end();
+});
+
+t.test("flattenSeedPermissions() inherits permissions from parent roles", t2 => {
 	const byName = new Map(seedRoles.map(role => [role.name, role]));
 	for (const role of seedRoles) {
 		if (role.parent === undefined) {
 			continue;
 		}
+
 		const parent = byName.get(role.parent);
-		subtest.ok(parent, `${role.name} has parent ${role.parent}`);
+		t2.ok(parent, `${role.name} has parent ${role.parent}`);
+
 		const flattened = flattenSeedPermissions(role);
 		for (const permission of flattenSeedPermissions(parent)) {
-			subtest.ok(flattened.has(permission), `${role.name} inherits ${permission}`);
+			t2.ok(flattened.has(permission), `${role.name} inherits ${permission}`);
 		}
 	}
-	subtest.end();
+	t2.end();
 });
 
-t.test("seedRoles are unique with one default and one admin", subtest => {
-	const names = seedRoles.map(role => role.name);
-	subtest.strictSame(names.length, new Set(names).size, "names are unique");
-	subtest.strictSame(seedRoles.filter(role => role.isDefault).length, 1, "one default role");
-	subtest.strictSame(seedRoles.filter(role => role.isAdmin).length, 1, "one admin role");
-	subtest.end();
-});
+t.test("flattenSeedPermissions() does not inherit permissions when parent is undefined", t2 => {
+	for (const role of seedRoles) {
+		if (role.parent !== undefined) {
+			continue;
+		}
+
+		const flattened = flattenSeedPermissions(role);
+		for (const permission of role.permissions) {
+			t2.ok(flattened.has(permission), `${role.name} contains ${permission}`);
+		}
+
+		t2.equal(
+			flattened.size,
+			role.permissions.length,
+			`${role.name} has no inherited permissions`,
+		);
+	}
+	t2.end();
+});
\ No newline at end of file
diff --git a/exp_scenario/module/control/nuke_protection.lua b/exp_scenario/module/control/nuke_protection.lua
index c8798388..ba8f4320 100644
--- a/exp_scenario/module/control/nuke_protection.lua
+++ b/exp_scenario/module/control/nuke_protection.lua
@@ -19,7 +19,7 @@ local function check_items(player, type, banned_items)
     local inventory = assert(player.get_inventory(type))
     -- Check what items the player has
     for i = 1, #inventory do
-        local item = inventory[i]
+        local item = inventory[i --[[@as uint]]]
         if item.valid_for_read and banned_items[item.name] then
             player.print{ "exp_nuke-protection.chat-found", item.prototype.localised_name }
             items[#items + 1] = item
diff --git a/exp_scenario/module/control/spawn_area.lua b/exp_scenario/module/control/spawn_area.lua
index aab08d17..d4c23275 100644
--- a/exp_scenario/module/control/spawn_area.lua
+++ b/exp_scenario/module/control/spawn_area.lua
@@ -5,8 +5,8 @@ Adds a custom spawn area with chests and afk turrets
 local config = require("modules.exp_legacy.config.spawn_area")
 
 --- Apply an offset to a LuaPosition
---- @param position MapPosition
---- @param offset MapPosition
+--- @param position MapPosition.struct
+--- @param offset MapPosition.struct
 --- @return MapPosition.struct
 local function apply_offset(position, offset)
     return {
@@ -17,7 +17,7 @@ end
 
 --- Apply offset to an array of positions
 --- @param positions table
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 --- @param x_index number
 --- @param y_index number
 local function apply_offset_to_array(positions, offset, x_index, y_index)
@@ -97,14 +97,19 @@ local belt_details = {
 
 --- Makes a 2x2 afk belt at the locations in the config
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_belts(surface, offset)
     local belt_type = config.afk_belts.belt_type
 
+    local entity_pos = { x = 0, y = 0 }
+    local group_offset = { x = 0, y = 0 }
     for _, position in pairs(config.afk_belts.locations) do
-        position = apply_offset(position, offset)
+        group_offset.x = position[1] + offset.x
+        group_offset.y = position[2] + offset.y
         for _, belt in pairs(belt_details) do
-            local pos = apply_offset(position, belt)
+            entity_pos.x = belt[1]
+            entity_pos.y = belt[2]
+            local pos = apply_offset(entity_pos, group_offset)
             local entity = surface.create_entity{ name = belt_type, position = pos, force = "neutral", direction = belt[3] }
             if entity and config.afk_belts.protected then
                 protect_entity(entity)
@@ -115,13 +120,16 @@ end
 
 -- Generates extra tiles in a set pattern as defined in the config
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_pattern_tiles(surface, offset)
     local tiles_to_make = {}
     local pattern_tile = config.pattern.pattern_tile
 
+    local tile_pos = { x = 0, y = 0 }
     for index, position in pairs(config.pattern.locations) do
-        tiles_to_make[index] = { name = pattern_tile, position = apply_offset(position, offset) }
+        tile_pos.x = position[1]
+        tile_pos.y = position[2]
+        tiles_to_make[index] = { name = pattern_tile, position = apply_offset(tile_pos, offset) }
     end
 
     surface.set_tiles(tiles_to_make)
@@ -129,13 +137,16 @@ end
 
 -- Generates extra water as defined in the config
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_water_tiles(surface, offset)
     local tiles_to_make = {}
     local water_tile = config.water.water_tile
 
+    local tile_pos = { x = 0, y = 0 }
     for _, position in pairs(config.water.locations) do
-        table.insert(tiles_to_make, { name = water_tile, position = apply_offset(position, offset) })
+        tile_pos.x = position[1]
+        tile_pos.y = position[2]
+        table.insert(tiles_to_make, { name = water_tile, position = apply_offset(tile_pos, offset) })
     end
 
     surface.set_tiles(tiles_to_make)
@@ -143,11 +154,17 @@ end
 
 --- Generates the entities that are in the config
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_entities(surface, offset)
+    local entity_pos = { x = 0, y = 0 }
     for _, entity_details in pairs(config.entities.locations) do
-        local pos = apply_offset({ entity_details[2], entity_details[3] }, offset)
-        local entity = surface.create_entity{ name = entity_details[1], position = pos, force = "neutral" }
+        entity_pos.x = entity_details[2]
+        entity_pos.y = entity_details[3]
+        local entity = surface.create_entity{
+            name = entity_details[1],
+            position = apply_offset(entity_pos, offset),
+            force = "neutral"
+        }
 
         if entity then
             if config.entities.protected then
@@ -161,7 +178,7 @@ end
 
 --- Generates an area with no water or entities, no water area is larger
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function clear_spawn_area(surface, offset)
     local get_tile = surface.get_tile
 
@@ -182,7 +199,7 @@ local function clear_spawn_area(surface, offset)
         for y = -fill_radius, fill_radius do -- loop over y
             local y_sqr = (y + 0.5) ^ 2
             local dst = x_sqr + y_sqr
-            local pos = apply_offset({ x, y }, offset)
+            local pos = apply_offset({ x = x, y = y }, offset)
             if dst < tile_radius_sqr then
                 -- If it is inside the decon radius always set the tile
                 tiles_to_make[#tiles_to_make + 1] = { name = decon_tile, position = pos }
@@ -204,14 +221,14 @@ end
 
 --- Spawn the resource tiles
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_resources_tiles(surface, offset)
     for _, resource in ipairs(config.resource_tiles.resources) do
         if resource.enabled then
             local pos = apply_offset(resource.offset, offset)
             for x = pos.x, pos.x + resource.size[1] do
                 for y = pos.y, pos.y + resource.size[2] do
-                    surface.create_entity{ name = resource.name, amount = resource.amount, position = { x, y } }
+                    surface.create_entity{ name = resource.name, amount = resource.amount, position = { x = x, y = y } }
                 end
             end
         end
@@ -220,7 +237,7 @@ end
 
 --- Spawn the resource entities
 --- @param surface LuaSurface
---- @param offset MapPosition
+--- @param offset MapPosition.struct
 local function create_resource_patches(surface, offset)
     for _, resource in ipairs(config.resource_patches.resources) do
         if resource.enabled then
diff --git a/exp_scenario/module/gui/module_inserter.lua b/exp_scenario/module/gui/module_inserter.lua
index ed320137..f930bd34 100644
--- a/exp_scenario/module/gui/module_inserter.lua
+++ b/exp_scenario/module/gui/module_inserter.lua
@@ -459,7 +459,7 @@ local function on_entity_settings_pasted(event)
         -- Get the modules and add them to the planner
         local all_modules = {}
         for i = 1, #module_inventory do
-            local slot = module_inventory[i]
+            local slot = module_inventory[i --[[@as uint]]]
             if slot.valid_for_read and slot.count > 0 then
                 all_modules[i] = { name = slot.name, quality = slot.quality.name }
             else
diff --git a/exp_scenario/module/gui/research_milestones.lua b/exp_scenario/module/gui/research_milestones.lua
index 390867c8..a7e06846 100644
--- a/exp_scenario/module/gui/research_milestones.lua
+++ b/exp_scenario/module/gui/research_milestones.lua
@@ -294,9 +294,9 @@ end
 --- Get the achieved time for a force
 --- @param force LuaForce
 --- @param research_index number
---- @return number
+--- @return number?
 function Elements.container.get_achieved_time(force, research_index)
-    return assert(Elements.container.data[force][research_index])
+    return assert(Elements.container.data[force])[research_index]
 end
 
 --- Calculate the starting research index for a force
diff --git a/test/common.js b/test/common.js
index eb75a3f2..bf63b030 100644
--- a/test/common.js
+++ b/test/common.js
@@ -1,5 +1,4 @@
 "use strict";
-const assert = require("assert").strict;
 const { compile } = require("@clusterio/lib");
 
 /**
@@ -15,22 +14,37 @@ function testMatrix(...arrays) {
 }
 
 /**
- * Test that a class is round trip json serialisable across multiple test cases.
+ * Test that a class is round trip JSON serialisable across multiple test cases.
  *
  * @template {any[]} T - Constructor arguments
+ * @param {import("tap").Test} t - Parent test.
  * @param {{new(...args: T): object}} Class - The class which has toJSON and fromJSON methods.
- * @param {T[]} tests - The tests inputs to pass to the class constructor.
+ * @param {T[]} tests - The test inputs to pass to the class constructor.
  */
-function testRoundTripJsonSerialisable(Class, tests) {
+function testRoundTripJsonSerialisable(t, Class, tests) {
 	const validate = compile(Class.jsonSchema);
+
 	for (const test of tests) {
-		const original = new Class(...test);
-		const serialised = JSON.stringify(original);
-		const jsonObject = JSON.parse(serialised);
-		const reconstructed = Class.fromJSON(jsonObject);
-		assert.deepEqual(reconstructed, original, JSON.stringify(test));
-		if (!validate(jsonObject)) {
-			throw validate.errors;
+		const name = JSON.stringify(test);
+
+		try {
+			const original = new Class(...test);
+			const jsonObject = JSON.parse(JSON.stringify(original));
+			const reconstructed = Class.fromJSON(jsonObject);
+
+			if (!validate(jsonObject)) {
+				t.fail(`schema validation: ${name}`, {
+					diagnostic: {
+						json: jsonObject,
+						errors: validate.errors,
+					},
+				});
+				continue;
+			}
+
+			t.strictSame(reconstructed, original, `round trip: ${name}`);
+		} catch (error) {
+			t.fail(`round trip: ${name}`, { error });
 		}
 	}
 }
diff --git a/test/lua/framework.lua b/test/lua/framework.lua
index eadca54c..9fc97207 100644
--- a/test/lua/framework.lua
+++ b/test/lua/framework.lua
@@ -10,6 +10,7 @@ local source = assert(debug.getinfo(1, "S")).source
 local shared_root = assert(source:match("^@(.*)/framework%.lua$"))
 local Stubs = assert(loadfile(shared_root .. "/stubs.lua"))()
 
+--- @class Framework
 local Framework = {}
 
 --- Turn a value into a string for failure messages
diff --git a/test/lua/stubs.lua b/test/lua/stubs.lua
index e587728e..3cc1b3a8 100644
--- a/test/lua/stubs.lua
+++ b/test/lua/stubs.lua
@@ -50,6 +50,7 @@ end
 
 --- Create an independent set of stubs, installed as the lua globals
 function Stubs.new()
+    --- @class Stubs
     local stubs = {
         events = {},  -- events raised through script.raise_event
         printed = {}, -- game.print and player.print messages