added tests for hostReducer and Header Effects, and switch to typed actions

src/app/header/header.actions.ts

@@ -1,24 +1,43 @@
 import { Action } from "@ngrx/store";
+import { type } from "../shared/ngrx/type";
 
-export class HeaderActions {
-  static COLLAPSE = 'dspace/header/COLLAPSE';
-  static collapse(): Action {
-    return {
-      type: HeaderActions.COLLAPSE
-    }
-  }
+ /**
+ * For each action type in an action group, make a simple
+ * enum object for all of this group's action types.
+ *
+ * The 'type' utility function coerces strings into string
+ * literal types and runs a simple check to guarantee all
+ * action types in the application are unique.
+ */
+export const HeaderActionTypes = {
+  COLLAPSE: type('dspace/header/COLLAPSE'),
+  EXPAND: type('dspace/header/EXPAND'),
+  TOGGLE: type('dspace/header/TOGGLE')
+};
 
-  static EXPAND = 'dspace/header/EXPAND';
-  static expand(): Action {
-    return {
-      type: HeaderActions.EXPAND
-    }
-  }
+export class HeaderCollapseAction implements Action {
+  type = HeaderActionTypes.COLLAPSE;
 
-  static TOGGLE = 'dspace/header/TOGGLE';
-  static toggle(): Action {
-    return {
-      type: HeaderActions.TOGGLE
-    }
-  }
+  constructor() {}
 }
+
+export class HeaderExpandAction implements Action {
+  type = HeaderActionTypes.EXPAND;
+
+  constructor() {}
+}
+
+export class HeaderToggleAction implements Action {
+  type = HeaderActionTypes.TOGGLE;
+
+  constructor() {}
+}
+
+/**
+ * Export a type alias of all actions in this action group
+ * so that reducers can easily compose action types
+ */
+export type HeaderAction
+  = HeaderCollapseAction
+  | HeaderExpandAction
+  | HeaderToggleAction