text: import { LagrangePolynomialApproximation } from '../../Source/Cesium.js';
  
  describe('Core/LagrangePolynomialApproximation', function() {
  
      //The results of these specs were validated against STK Components
      //an aerospace SDK available from Analytical Graphics. www.agi.com/components/
  
      var xTable = [0, 60, 120, 180, 240, 300, 360, 420];
      var yTable = [
                    13378137.0000000, 0.000000000, 0,
                    13374128.3576279, 327475.593690065, 0,
                    13362104.8328212, 654754.936954423, 0,
                    13342073.6310691, 981641.896976832, 0,
                    13314046.7567223, 1307940.576089510, 0,
                    13278041.0057990, 1633455.429171170, 0,
                    13234077.9559193, 1957991.380833850, 0,
                    13182183.9533740, 2281353.942328160, 0
                   ];
  
      var x = 100.0;
  
      it('interpolation produces correct results.', function() {
          var result = LagrangePolynomialApproximation.interpolateOrderZero(x, xTable, yTable, 3);
          var expectedResult = [13367002.870928623, 545695.7388100647, 0];
          expect(result).toEqualEpsilon(expectedResult, 1e-15);
      });
  
      it('interpolation produces correct results with a result parameter', function() {
          var result = new Array(3);
          var returnedResult = LagrangePolynomialApproximation.interpolateOrderZero(x, xTable, yTable, 3, result);
          var expectedResult = [13367002.870928623, 545695.7388100647, 0];
          expect(result).toBe(returnedResult);
          expect(result).toEqualEpsilon(expectedResult, 1e-15);
      });
  
      it('getRequiredDataPoints should be 1 more than degree, except for 0, which requires 2', function() {
          expect(LagrangePolynomialApproximation.getRequiredDataPoints(0)).toEqual(2);
          expect(LagrangePolynomialApproximation.getRequiredDataPoints(1)).toEqual(2);
          expect(LagrangePolynomialApproximation.getRequiredDataPoints(2)).toEqual(3);
          expect(LagrangePolynomialApproximation.getRequiredDataPoints(3)).toEqual(4);
      });
  });
  