Add tests and split methods in `ChartPanel`

[j-mortara]

Class description

Class full name

org.jfree.chart.ChartPanel

Implemented variability :heavy_check_mark:

This class represents where the chart with all its elements will be rendered

Method level:

5 constructors

1. create the Panel
2. create the Panel using a buffer to speed up repainting
3. create the Panel and specify which buttons should appear on the window (save, print, zoom, tooltips, properties editor)
4. same as 3. and specifying maximum dimensions
5. same as 4. + copy option on the window

6 method variants

• zoomInFactor (2×): zoom in a chart
• zoomOutFactor (2×): zoom out a chart
• createPopupMenu (2×): creates a popup menu, for saving for example (they correspond to the options that can be chosen when creating the Panel using constructors 3. to 5.

  Class level: 1 subclass for the polar plot, which has adapted zoom and auto range implementations.

Actual coverage (JaCoCo)

• methods: 25%
• lines: 31%

Visualization

• fade: coverage
• cracks: cognitive complexity

TODO

Split the most cognitively complex methods

• [ ] getToolTipText
• [ ] paintComponent
• [ ] actionPerformed
• [ ] mousePressed
• [ ] mouseDragged
• [ ] createPopupMenu

Add tests for the following methods that are currently not or partially covered

• [x] getToolTipText
• [x] scale
• [ ] generateSVG
• [ ] createSGGraphics2D

Other methods are not tested, but are fully dedicated to graphical behavior, so they might be hard to test

• [ ] paintComponent
• [x] actionPerformed
• [x] mousePressed
• [ ] mouseDragged

[collet]

getToolTipText is not that complex.

[collet]

For the graphical behavior method, there are indeed very hard to understand and we observe that:

• none of the 3 paintComponent methods in 3 classes are tested
• none of the 11 actionPerformed methods in 11 classes are testes
• mousePressed and mouseDragged event listener methods are only used in ChartPanel but cannot be easily test for the same reason (the need to reproduce or mock the full graphical stack)

[collet]

https://stackoverflow.com/questions/329118/how-do-i-activate-jbutton-actionlistener-inside-code-unit-testing-purposes https://stackoverflow.com/questions/62614105/how-to-junit-test-an-actionlistener

[collet]

https://stackoverflow.com/questions/8986368/junit-testing-overridden-paint-component