Enable the no-undef eslint rule (#1848)

## Description:

Enable the `no-undef` eslint rule.

Fixes #1786

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

tests/MissileSilo.test.ts

@@ -91,7 +91,7 @@ describe("MissileSilo", () => {
   });
 
   test("missilesilo should have increased level after upgrade", async () => {
-    expect(attacker.units(UnitType.MissileSilo)[0].level()).toEqual(1);
+    expect(attacker.units(UnitType.MissileSilo)[0].level()).toBe(1);
 
     const upgradeStructureExecution = new UpgradeStructureExecution(
       attacker,
@@ -100,6 +100,6 @@ describe("MissileSilo", () => {
     game.addExecution(upgradeStructureExecution);
     executeTicks(game, 2);
 
-    expect(attacker.units(UnitType.MissileSilo)[0].level()).toEqual(2);
+    expect(attacker.units(UnitType.MissileSilo)[0].level()).toBe(2);
   });
 });

tests/PlayerImpl.test.ts

@@ -96,7 +96,7 @@ describe("PlayerImpl", () => {
 
     const ports = player.tradingPorts(playerPort);
 
-    expect(ports.length).toBe(3);
+    expect(ports).toHaveLength(3);
   });
 
   test("Can't send alliance requests when dead", () => {

tests/TeamAssignment.test.ts

@@ -83,7 +83,7 @@ describe("assignTeams", () => {
     expect(result.get(players[1])).toEqual(ColoredTeams.Red);
     expect(result.get(players[2])).toEqual(ColoredTeams.Red);
 
-    expect(result.get(players[3])).toEqual("kicked");
+    expect(result.get(players[3])).toBe("kicked");
 
     expect(result.get(players[4])).toEqual(ColoredTeams.Blue);
     expect(result.get(players[5])).toEqual(ColoredTeams.Blue);
@@ -151,7 +151,7 @@ describe("assignTeams", () => {
 
     expect(result.get(players[0])).toEqual(ColoredTeams.Red);
     expect(result.get(players[1])).toEqual(ColoredTeams.Red);
-    expect(result.get(players[2])).toEqual("kicked");
+    expect(result.get(players[2])).toBe("kicked");
     expect(result.get(players[3])).toEqual(ColoredTeams.Blue);
     expect(result.get(players[4])).toEqual(ColoredTeams.Blue);
     expect(result.get(players[5])).toEqual(ColoredTeams.Yellow);

tests/UnitGrid.test.ts

@@ -90,7 +90,7 @@ describe("Unit Grid range tests", () => {
           range,
           units, // remove readonly
         );
-        expect(result.length).toBe(expectedResult);
+        expect(result).toHaveLength(expectedResult);
       },
     );
 

tests/core/executions/SAMLauncherExecution.test.ts

@@ -230,7 +230,7 @@ describe("SAM", () => {
 
   test("SAM should have increased level after upgrade", async () => {
     defender.buildUnit(UnitType.SAMLauncher, game.ref(1, 1), {});
-    expect(defender.units(UnitType.SAMLauncher)[0].level()).toEqual(1);
+    expect(defender.units(UnitType.SAMLauncher)[0].level()).toBe(1);
 
     const upgradeStructureExecution = new UpgradeStructureExecution(
       defender,
@@ -239,6 +239,6 @@ describe("SAM", () => {
     game.addExecution(upgradeStructureExecution);
     executeTicks(game, 2);
 
-    expect(defender.units(UnitType.SAMLauncher)[0].level()).toEqual(2);
+    expect(defender.units(UnitType.SAMLauncher)[0].level()).toBe(2);
   });
 });

tests/core/game/RailNetwork.test.ts

@@ -42,7 +42,7 @@ describe("StationManagerImpl", () => {
     const station = createMockStation(1);
     manager.addStation(station);
     manager.removeStation(station);
-    expect(manager.findStation(station.unit)).toBe(null);
+    expect(manager.findStation(station.unit)).toBeNull();
   });
 });