refactor: Improve Code Readability and Maintainability

In this commit, I've made the following enhancements to the code:
1. Change the test case of finding the disabled time units count to the finding the enabled time units as the module involves on the existence of the includeTimes
2. Moved the test case to find the enabled time units through aria-disabled attribute to the separate it block
3. Replaced the magic value 45 with the actual computation which resolves to the magic value, to make it more maintainable and readable

Closes Hacker0x01#4334

test/include_times_test.test.js

@@ -4,26 +4,54 @@ import * as utils from "../src/date_utils";
 import TimeComponent from "../src/time";
 
 describe("TimeComponent", () => {
+  let today, includeTimes;
+
+  beforeEach(() => {
+    today = utils.getStartOfDay(utils.newDate());
+    includeTimes = [
+      utils.addMinutes(today, 60),
+      utils.addMinutes(today, 120),
+      utils.addMinutes(today, 150),
+    ];
+  });
+
   it("should only enable times specified in includeTimes props", () => {
-    const today = utils.getStartOfDay(utils.newDate());
     const { container: timeComponent } = render(
-      <TimeComponent
-        includeTimes={[
-          utils.addMinutes(today, 60),
-          utils.addMinutes(today, 120),
-          utils.addMinutes(today, 150),
-        ]}
-      />,
+      <TimeComponent includeTimes={includeTimes} />,
     );
 
+    const allTimeItems = timeComponent.querySelectorAll(
+      ".react-datepicker__time-list-item",
+    );
     const disabledTimeItems = timeComponent.querySelectorAll(
       ".react-datepicker__time-list-item--disabled",
     );
-    expect(disabledTimeItems.length).toBe(45);
 
-    const allDisabledTimeItemsHaveAriaDisabled = Array.from(
-      disabledTimeItems,
-    ).every((time) => time.getAttribute("aria-disabled") === "true");
-    expect(allDisabledTimeItemsHaveAriaDisabled).toBe(true);
+    const expectedDisabledTimeItems = allTimeItems.length - includeTimes.length;
+    expect(disabledTimeItems.length).toBe(expectedDisabledTimeItems);
+  });
+
+  it("should not add aria-disabled attribute on all the enabled times", () => {
+    const { container: timeComponent } = render(
+      <TimeComponent includeTimes={includeTimes} />,
+    );
+
+    const allTimeItems = timeComponent.querySelectorAll(
+      ".react-datepicker__time-list-item",
+    );
+    const enabledTimeItems = Array.from(allTimeItems).filter(
+      (timeItem) =>
+        !timeItem.classList.contains(
+          "react-datepicker__time-list-item--disabled",
+        ),
+    );
+
+    const enabledTimeItemsHasNoAriaDisabled = Array.from(
+      enabledTimeItems,
+    ).every((timeItem) => {
+      const ariaDisabledValue = timeItem.getAttribute("aria-disabled");
+      return !ariaDisabledValue || ariaDisabledValue.toLowerCase() === "false";
+    });
+    expect(enabledTimeItemsHasNoAriaDisabled).toBe(true);
   });
 });