more testing

testing/__tests__/image_scaler_test.lua

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+local luaunit = require("testing.luaunit")
+require("testing.loveStub")
+
+local ImageScaler = require("modules.ImageScaler")
+
+TestImageScaler = {}
+
+function TestImageScaler:setUp()
+  -- Create a minimal mock ImageData
+  self.mockImageData = {
+    getPixel = function(self, x, y)
+      -- Return deterministic values based on position
+      return (x % 256) / 255, (y % 256) / 255, 0.5, 1.0
+    end,
+  }
+end
+
+-- Unhappy path tests for scaleNearest
+
+function TestImageScaler:testScaleNearestWithNilSource()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(nil, 0, 0, 10, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithZeroSourceWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 0, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithZeroSourceHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, 0, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithNegativeSourceWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, -10, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithNegativeSourceHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, -10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithZeroDestWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, 10, 0, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithZeroDestHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, 10, 20, 0)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithNegativeDestWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, 10, -20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleNearestWithNegativeDestHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleNearest(self.mockImageData, 0, 0, 10, 10, 20, -20)
+  end)
+end
+
+-- Unhappy path tests for scaleBilinear
+
+function TestImageScaler:testScaleBilinearWithNilSource()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(nil, 0, 0, 10, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithZeroSourceWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 0, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithZeroSourceHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, 0, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithNegativeSourceWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, -10, 10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithNegativeSourceHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, -10, 20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithZeroDestWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, 10, 0, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithZeroDestHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, 10, 20, 0)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithNegativeDestWidth()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, 10, -20, 20)
+  end)
+end
+
+function TestImageScaler:testScaleBilinearWithNegativeDestHeight()
+  luaunit.assertError(function()
+    ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 10, 10, 20, -20)
+  end)
+end
+
+-- Edge case tests
+
+function TestImageScaler:testScaleNearestWithVeryLargeUpscale()
+  -- Scale 1x1 to 50x50 (extreme upscale, but fast for testing)
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 1, 1, 50, 50)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWithVeryLargeDownscale()
+  -- Scale 50x50 to 1x1 (extreme downscale)
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 50, 50, 1, 1)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWithVeryLargeUpscale()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 1, 1, 50, 50)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWithVeryLargeDownscale()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 50, 50, 1, 1)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWithNonIntegerDimensions()
+  -- Fractional source dimensions (should work with floor/ceil)
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 5.5, 5.5, 10, 10)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWithNonIntegerDimensions()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 5.5, 5.5, 10, 10)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWith1x1Source()
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 1, 1, 5, 5)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWith1x1Source()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 1, 1, 5, 5)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWith1x1Dest()
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 5, 5, 1, 1)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWith1x1Dest()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 5, 5, 1, 1)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWithNonZeroSourceOffset()
+  -- Source region offset from 0,0
+  local result = ImageScaler.scaleNearest(self.mockImageData, 10, 10, 5, 5, 10, 10)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWithNonZeroSourceOffset()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 10, 10, 5, 5, 10, 10)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleNearestWithAspectRatioChange()
+  -- Change aspect ratio dramatically
+  local result = ImageScaler.scaleNearest(self.mockImageData, 0, 0, 5, 20, 20, 5)
+  luaunit.assertNotNil(result)
+end
+
+function TestImageScaler:testScaleBilinearWithAspectRatioChange()
+  local result = ImageScaler.scaleBilinear(self.mockImageData, 0, 0, 5, 20, 20, 5)
+  luaunit.assertNotNil(result)
+end
+
+if not _G.RUNNING_ALL_TESTS then
+  os.exit(luaunit.LuaUnit.run())
+end