Add tests for CombatLayer.

client/src/components/combatlayer/CombatLayer.test.tsx

@@ -0,0 +1,48 @@
+import { renderWithProviders } from "../../testutils";
+import CombatLayer from "./CombatLayer";
+import { LatLng } from "leaflet";
+import { PropsWithChildren } from "react";
+
+const mockPolyline = jest.fn();
+const mockLayerGroup = jest.fn();
+jest.mock("react-leaflet", () => ({
+  LayerGroup: (props: PropsWithChildren<any>) => {
+    mockLayerGroup(props);
+    return <>{props.children}</>;
+  },
+  Polyline: (props: any) => {
+    mockPolyline(props);
+  },
+}));
+
+describe("CombatLayer", () => {
+  it("renders each combat", () => {
+    renderWithProviders(<CombatLayer />, {
+      preloadedState: {
+        combat: {
+          combat: {
+            foo: {
+              id: "foo",
+              flight_position: new LatLng(0, 0),
+              target_positions: [new LatLng(0, 1)],
+              footprint: null,
+            },
+            bar: {
+              id: "foo",
+              flight_position: new LatLng(0, 0),
+              target_positions: [new LatLng(0, 1)],
+              footprint: null,
+            },
+          },
+        },
+      },
+    });
+    expect(mockPolyline).toBeCalledTimes(2);
+  });
+
+  it("renders LayerGroup but no contents if no combat", () => {
+    renderWithProviders(<CombatLayer />);
+    expect(mockLayerGroup).toBeCalledTimes(1);
+    expect(mockPolyline).not.toHaveBeenCalled();
+  });
+});