Migrate doctest for Mandelbrot.js

(also remove inline test driver code & moved manual drawing test into a *.manual-test.js)

Maths/Mandelbrot.js

@@ -1,54 +1,33 @@
 /**
- * The Mandelbrot set is the set of complex numbers "c" for which the series "z_(n+1) = z_n * z_n +
- * c" does not diverge, i.e. remains bounded. Thus, a complex number "c" is a member of the
- * Mandelbrot set if, when starting with "z_0 = 0" and applying the iteration repeatedly, the
- * absolute value of "z_n" remains bounded for all "n > 0". Complex numbers can be written as "a +
- * b*i": "a" is the real component, usually drawn on the x-axis, and "b*i" is the imaginary
- * component, usually drawn on the y-axis. Most visualizations of the Mandelbrot set use a
- * color-coding to indicate after how many steps in the series the numbers outside the set cross the
- * divergence threshold. Images of the Mandelbrot set exhibit an elaborate and infinitely
- * complicated boundary that reveals progressively ever-finer recursive detail at increasing
- * magnifications, making the boundary of the Mandelbrot set a fractal curve. (description adapted
- * from https://en.wikipedia.org/wiki/Mandelbrot_set ) (see also
- * https://en.wikipedia.org/wiki/Plotting_algorithms_for_the_Mandelbrot_set )
- */
-
-/*
-Doctests
-Test black and white
-Pixel outside the Mandelbrot set should be white.
-Pixel inside the Mandelbrot set should be black.
-> getRGBData(800, 600, -0.6, 0, 3.2, 50, false)[0][0]
-[255, 255, 255]
-> getRGBData(800, 600, -0.6, 0, 3.2, 50, false)[400][300]
-[0, 0, 0]
-
-Test color-coding
-Pixel distant to the Mandelbrot set should be red.
-Pixel inside the Mandelbrot set should be black.
-> getRGBData(800, 600, -0.6, 0, 3.2, 50, true)[0][0]
-[255, 0, 0]
-> getRGBData(800, 600, -0.6, 0, 3.2, 50, true)[400][300]
-[0, 0, 0]
-*/
-
-/**
- * Method to generate the image of the Mandelbrot set. Two types of coordinates are used:
- * image-coordinates that refer to the pixels and figure-coordinates that refer to the complex
- * numbers inside and outside the Mandelbrot set. The figure-coordinates in the arguments of this
- * method determine which section of the Mandelbrot set is viewed. The main area of the Mandelbrot
- * set is roughly between "-1.5 < x < 0.5" and "-1 < y < 1" in the figure-coordinates.
+ * Method to generate the image of the Mandelbrot set.
+ *
+ * Two types of coordinates are used: image-coordinates that refer to the pixels and figure-coordinates that refer to
+ * the complex numbers inside and outside the Mandelbrot set. The figure-coordinates in the arguments of this method
+ * determine which section of the Mandelbrot set is viewed. The main area of the Mandelbrot set is roughly between
+ * "-1.5 < x < 0.5" and "-1 < y < 1" in the figure-coordinates.
+ *
+ * The Mandelbrot set is the set of complex numbers "c" for which the series "z_(n+1) = z_n * z_n + c" does not diverge,
+ * i.e. remains bounded. Thus, a complex number "c" is a member of the Mandelbrot set if, when starting with "z_0 = 0"
+ * and applying the iteration repeatedly, the absolute value of "z_n" remains bounded for all "n > 0". Complex numbers
+ * can be written as "a + b*i": "a" is the real component, usually drawn on the x-axis, and "b*i" is the imaginary
+ * component, usually drawn on the y-axis. Most visualizations of the Mandelbrot set use a color-coding to indicate
+ * after how many steps in the series the numbers outside the set cross the divergence threshold. Images of the
+ * Mandelbrot set exhibit an elaborate and infinitely complicated boundary that reveals progressively ever-finer
+ * recursive detail at increasing magnifications, making the boundary of the Mandelbrot set a fractal curve.
+ *
+ * (description adapted from https://en.wikipedia.org/wiki/Mandelbrot_set)
+ * @see https://en.wikipedia.org/wiki/Plotting_algorithms_for_the_Mandelbrot_set
  *
  * @param {number} imageWidth The width of the rendered image.
  * @param {number} imageHeight The height of the rendered image.
  * @param {number} figureCenterX The x-coordinate of the center of the figure.
  * @param {number} figureCenterY The y-coordinate of the center of the figure.
  * @param {number} figureWidth The width of the figure.
  * @param {number} maxStep Maximum number of steps to check for divergent behavior.
- * @param {number} useDistanceColorCoding Render in color or black and white.
+ * @param {boolean} useDistanceColorCoding Render in color or black and white.
  * @return {object} The RGB-data of the rendered Mandelbrot set.
  */
-function getRGBData (
+export function getRGBData (
  imageWidth = 800,
  imageHeight = 600,
  figureCenterX = -0.6,
@@ -83,18 +62,19 @@ function getRGBData (
 
  // color the corresponding pixel based on the selected coloring-function
  rgbData[imageX][imageY] =
-  useDistanceColorCoding
-  ? colorCodedColorMap(distance)
-  : blackAndWhiteColorMap(distance)
+ useDistanceColorCoding
+ ? colorCodedColorMap(distance)
+ : blackAndWhiteColorMap(distance)
  }
  }
 
  return rgbData
 }
 
 /**
- * Black and white color-coding that ignores the relative distance. The Mandelbrot set is black,
- * everything else is white.
+ * Black and white color-coding that ignores the relative distance.
+ *
+ * The Mandelbrot set is black, everything else is white.
  *
  * @param {number} distance Distance until divergence threshold
  * @return {object} The RGB-value corresponding to the distance.
@@ -104,7 +84,9 @@ function blackAndWhiteColorMap (distance) {
 }
 
 /**
- * Color-coding taking the relative distance into account. The Mandelbrot set is black.
+ * Color-coding taking the relative distance into account.
+ *
+ * The Mandelbrot set is black.
  *
  * @param {number} distance Distance until divergence threshold
  * @return {object} The RGB-value corresponding to the distance.
@@ -145,11 +127,12 @@ function colorCodedColorMap (distance) {
 
 /**
  * Return the relative distance (ratio of steps taken to maxStep) after which the complex number
- * constituted by this x-y-pair diverges. Members of the Mandelbrot set do not diverge so their
- * distance is 1.
+ * constituted by this x-y-pair diverges.
+ *
+ * Members of the Mandelbrot set do not diverge so their distance is 1.
  *
  * @param {number} figureX The x-coordinate within the figure.
- * @param {number} figureX The y-coordinate within the figure.
+ * @param {number} figureY The y-coordinate within the figure.
  * @param {number} maxStep Maximum number of steps to check for divergent behavior.
  * @return {number} The relative distance as the ratio of steps taken to maxStep.
  */
@@ -171,22 +154,3 @@ function getDistance (figureX, figureY, maxStep) {
  }
  return currentStep / (maxStep - 1)
 }
-
-// plot the results if the script is executed in a browser with a window-object
-if (typeof window !== 'undefined') {
- const rgbData = getRGBData()
- const width = rgbData.length
- const height = rgbData[0].length
- const canvas = document.createElement('canvas')
- canvas.width = width
- canvas.height = height
- const ctx = canvas.getContext('2d')
- for (let x = 0; x < width; x++) {
- for (let y = 0; y < height; y++) {
- const rgb = rgbData[x][y]
- ctx.fillStyle = 'rgb(' + rgb[0] + ',' + rgb[1] + ',' + rgb[2] + ')'
- ctx.fillRect(x, y, 1, 1)
- }
- }
- document.body.append(canvas)
-}

Maths/test/Mandelbrot.manual-test.js

@@ -0,0 +1,20 @@
+import { getRGBData } from '../Mandelbrot'
+
+// plot the results if the script is executed in a browser with a window-object
+if (typeof window !== 'undefined') {
+ const rgbData = getRGBData()
+ const width = rgbData.length
+ const height = rgbData[0].length
+ const canvas = document.createElement('canvas')
+ canvas.width = width
+ canvas.height = height
+ const ctx = canvas.getContext('2d')
+ for (let x = 0; x < width; x++) {
+ for (let y = 0; y < height; y++) {
+ const rgb = rgbData[x][y]
+ ctx.fillStyle = 'rgb(' + rgb[0] + ',' + rgb[1] + ',' + rgb[2] + ')'
+ ctx.fillRect(x, y, 1, 1)
+ }
+ }
+ document.body.append(canvas)
+}

Maths/test/Mandelbrot.test.js

@@ -0,0 +1,21 @@
+import { getRGBData } from '../Mandelbrot'
+
+describe('Mandelbrot', () => {
+ it('should produce black pixels inside the set', () => {
+ const blackAndWhite = getRGBData(800, 600, -0.6, 0, 3.2, 50, false)
+ expect(blackAndWhite[400][300]).toEqual([0, 0, 0]) // black
+
+ const colorCoded = getRGBData(800, 600, -0.6, 0, 3.2, 50, true)
+ expect(colorCoded[400][300]).toEqual([0, 0, 0]) // black
+ })
+
+ it('should produce white pixels outside of the set', () => {
+ const blackAndWhite = getRGBData(800, 600, -0.6, 0, 3.2, 50, false)
+ expect(blackAndWhite[0][0]).toEqual([255, 255, 255]) // black
+ })
+
+ it('should produce colored pixels distant to the set', () => {
+ const colorCoded = getRGBData(800, 600, -0.6, 0, 3.2, 50, true)
+ expect(colorCoded[0][0]).toEqual([255, 0, 0]) // red
+ })
+})