@alliumlabs/panchanga-ts/src/__tests__/calculations/nakshatra.test.ts

A TypeScript library for Hindu calendar (Panchanga) calculations including tithis, nakshatras, and other astronomical elements

import { AstroTime, Observer } from "astronomy-engine";
import { computeNakshatra } from "../../calculations/nakshatra";

describe("Nakshatra Calculations", () => {
  // Setup a standard observer for tests (Bangalore, India)
  const observer: Observer = new Observer(
    12.9716,
    77.5946,
    920 // meters above sea level
  );

  test("correctly calculates nakshatra for a given time and observer", async () => {
    // Use a specific date for testing
    const date = new Date(2023, 0, 1, 6, 0, 0); // January 1, 2023, 6:00 AM local time
    const time = new AstroTime(date);

    const result = await computeNakshatra(time, observer);

    // Basic validity checks
    expect(typeof result.index).toBe("number");
    expect(result.index).toBeGreaterThanOrEqual(1);
    expect(result.index).toBeLessThanOrEqual(27);
    expect(result.endTime instanceof AstroTime).toBe(true);
    expect(typeof result.description).toBe("string");
  });

  test("ensures the nakshatra index is always between 1 and 27", async () => {
    const testDates = [
      new AstroTime(new Date(2023, 0, 1, 6, 0, 0)),
      new AstroTime(new Date(2023, 3, 15, 6, 0, 0)),
      new AstroTime(new Date(2023, 6, 15, 6, 0, 0)),
      new AstroTime(new Date(2023, 9, 15, 6, 0, 0)),
    ];

    for (const date of testDates) {
      const result = await computeNakshatra(date, observer);
      expect(result.index).toBeGreaterThanOrEqual(1);
      expect(result.index).toBeLessThanOrEqual(27);
    }
  });

  test("calculates nakshatra end time later than input time", async () => {
    const time = new AstroTime(new Date(2023, 0, 1, 6, 0, 0));

    const result = await computeNakshatra(time, observer);

    expect(result.endTime!.ut > time.ut).toBe(true);
    // End time should generally be less than 24 hours from start time
    expect(result.endTime!.ut - time.ut).toBeLessThan(1.15);
  });
});