From f77390ce1d6c5ee4ee3ce6344c85a6fba3329814 Mon Sep 17 00:00:00 2001
From: Theodore Kruczek <theodore.kruczek@gmail.com>
Date: Sun, 14 Jan 2024 16:48:03 -0500
Subject: [PATCH] test: :white_check_mark: add tests for J2000

---
 src/coordinate/J2000.ts       | 26 ++++++++++++-
 test/coordinate/J2000.test.ts | 70 +++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 1 deletion(-)
 create mode 100644 test/coordinate/J2000.test.ts

diff --git a/src/coordinate/J2000.ts b/src/coordinate/J2000.ts
index f7af5e6..2792025 100644
--- a/src/coordinate/J2000.ts
+++ b/src/coordinate/J2000.ts
@@ -5,9 +5,23 @@ import { ITRF } from './ITRF';
 import { StateVector } from './StateVector';
 import { TEME } from './TEME';
 
+/**
+ * Represents a position and velocity in the J2000 coordinate system. This is an
+ * Earth-centered inertial (ECI) coordinate system.
+ *
+ * Commonly used ECI frame is defined with the Earth's Mean Equator and Mean
+ * Equinox (MEME) at 12:00 Terrestrial Time on 1 January 2000. It can be
+ * referred to as J2K, J2000 or EME2000. The x-axis is aligned with the mean
+ * vernal equinox. The z-axis is aligned with the Earth's rotation axis (or
+ * equivalently, the celestial North Pole) as it was at that time. The y-axis is
+ * rotated by 90° East about the celestial equator.
+ *
+ * @see https://en.wikipedia.org/wiki/Earth-centered_inertial
+ */
 export class J2000 extends StateVector {
   /**
-   * Creates a J2000 instance from classical elements.
+   * Creates a J2000 coordinate from classical elements.
+   * @param elements The classical elements. @returns The J2000 coordinate.
    */
   static fromClassicalElements(elements: ClassicalElements): J2000 {
     const rv = elements.toPositionVelocity();
@@ -17,6 +31,7 @@ export class J2000 extends StateVector {
 
   /**
    * Gets the name of the coordinate system.
+   * @returns The name of the coordinate system.
    */
   get name(): string {
     return 'J2000';
@@ -24,6 +39,8 @@ export class J2000 extends StateVector {
 
   /**
    * Gets a value indicating whether the coordinate system is inertial.
+   * @returns A boolean value indicating whether the coordinate system is
+   * inertial.
    */
   get inertial(): boolean {
     return true;
@@ -34,6 +51,8 @@ export class J2000 extends StateVector {
    * Reference Frame (ITRF).
    *
    * This is an ECI to ECF transformation.
+   *
+   * @returns The ITRF coordinates.
    */
   toITRF(): ITRF {
     const p = Earth.precession(this.epoch);
@@ -49,6 +68,11 @@ export class J2000 extends StateVector {
     return new ITRF(this.epoch, rPEF, vPEF);
   }
 
+  /**
+   * Converts the J2000 coordinate to the TEME coordinate.
+   *
+   * @returns The TEME coordinate.
+   */
   toTEME(): TEME {
     const p = Earth.precession(this.epoch);
     const n = Earth.nutation(this.epoch);
diff --git a/test/coordinate/J2000.test.ts b/test/coordinate/J2000.test.ts
new file mode 100644
index 0000000..560710a
--- /dev/null
+++ b/test/coordinate/J2000.test.ts
@@ -0,0 +1,70 @@
+// Generated by CodiumAI
+
+import { EpochUTC, ClassicalElements, Kilometers, Radians, J2000, Vector3D } from '../../src/main';
+import { exampleDate } from '../lib/mockData';
+
+describe('J2000', () => {
+  const epoch = EpochUTC.fromDateTime(exampleDate);
+
+  // can be created from classical elements
+  it('should create a J2000 coordinate from classical elements', () => {
+    const elements = new ClassicalElements({
+      epoch,
+      semimajorAxis: 6943.547853722985 as Kilometers,
+      eccentricity: 0.0011235968124658146,
+      inclination: 0.7509087232045765 as Radians,
+      rightAscension: 0.028239555738616327 as Radians,
+      argPerigee: 2.5386411901807353 as Radians,
+      trueAnomaly: 0.5931399364974058 as Radians,
+    });
+    const j2000 = J2000.fromClassicalElements(elements);
+
+    expect(j2000.epoch).toEqual(elements.epoch);
+    expect(j2000.position).toEqual(elements.toPositionVelocity().position);
+    expect(j2000.velocity).toEqual(elements.toPositionVelocity().velocity);
+  });
+
+  // can get the name of the coordinate system
+  it('should return the name of the coordinate system as "J2000"', () => {
+    const j2000 = new J2000(
+      epoch,
+      new Vector3D<Kilometers>(5000 as Kilometers, 10000 as Kilometers, 2100 as Kilometers),
+      new Vector3D<Kilometers>(7 as Kilometers, 4 as Kilometers, 2 as Kilometers),
+    );
+
+    expect(j2000.name).toBe('J2000');
+  });
+
+  // can get a value indicating whether the coordinate system is inertial
+  it('should return true for the inertial property', () => {
+    const j2000 = new J2000(
+      epoch,
+      new Vector3D<Kilometers>(5000 as Kilometers, 10000 as Kilometers, 2100 as Kilometers),
+      new Vector3D<Kilometers>(7 as Kilometers, 4 as Kilometers, 2 as Kilometers),
+    );
+
+    expect(j2000.inertial).toBe(true);
+  });
+
+  // Check conversion to and from
+  it('should convert to and from other coordinate systems', () => {
+    const j2000 = new J2000(
+      epoch,
+      new Vector3D<Kilometers>(5000 as Kilometers, 10000 as Kilometers, 2100 as Kilometers),
+      new Vector3D<Kilometers>(7 as Kilometers, 4 as Kilometers, 2 as Kilometers),
+    );
+    const itrf = j2000.toITRF();
+    const j200FromItf = itrf.toJ2000();
+
+    expect(j200FromItf.position.x).toBeCloseTo(j2000.position.x, 8);
+    expect(j200FromItf.position.y).toBeCloseTo(j2000.position.y, 8);
+    expect(j200FromItf.position.z).toBeCloseTo(j2000.position.z, 8);
+
+    const teme = j2000.toTEME();
+    const j200FromTeme = teme.toJ2000();
+
+    expect(j200FromTeme.position.x).toBeCloseTo(j2000.position.x, 8);
+    expect(j200FromTeme.position.y).toBeCloseTo(j2000.position.y, 8);
+    expect(j200FromTeme.position.z).toBeCloseTo(j2000.position.z, 8);
+  });
+});