Verify that test output files actually match the reference files (#59)

* Verify that images produced by tests exactly match their reference files.

There are only 3 failures, which is rather good.
- 2 Histogram step graphs. The reference images likely predate the recent bug-fix and need updating.
- Nested subplots. The scale on the Y axis appears to have increased. Investigating.

* Verified that histogram failures are due to recent bug fix:
- SVG output is correct.
- Difference is only in the stacked histogram, which has become a bit shorter since it's no longer accumulating state from previous renders.

* Manually confirmed that function plot failure on CoreGraphics is due to addition of "clampY" parameter by reverting to the old algorithm and having it pass.
19b308b updated the reference for the other images, but missed CG. Updating that image now.

* Verified that subplot test failure was due to randomness in the dataset. Replaced it with a repeatable pattern.

* Improved the base64 encoding test. Actually, to the extent that we seem to have found a massive bug (which hasn't been fixed, so this test now XFAILs).
We know from the original BarChart test that the AGG renderer produces identical binary files when writing to disk - however, when encoding both images, they do not encode to the same output.
Moreover, the test output appears invalid and many browsers do not seem to want to render it.

* Update SVG reference files for f309cf4

Semi-colons matter!

Author: karwa

Tests/SwiftPlotTests/AGGRenderer/agg-png-output.swift

@@ -4,40 +4,42 @@ import SwiftPlot
 import AGGRenderer
 
 extension AGGRendererTests {
+  
+  /// **XFAIL**
+  ///
+  /// Tests that base64 encoding is accurate by drawing a known graph directly in to
+  /// a PNG buffer (no files), then verifying the base64-encoded data matches that from
+  /// the reference file.
+  func testBase64Encoding() throws {
 
-    func testBase64Encoding() {
-        let renderer = AGGRenderer()
-        let rect = Rect(origin: zeroPoint, size: Size(width: 200, height: 200))
-        
-        renderer.imageSize = rect.size
-        renderer.drawSolidRect(rect, fillColor: .white, hatchPattern: .none)
-        renderer.drawSolidCircle(center: Point(100,100), radius: 75, fillColor: .red)
-        
-        let png = renderer.base64Png()
-        XCTAssertEqual(png.count, 2315)
-        
-        // Check that we can decode it again.
-        guard let data = Data(base64Encoded: png, options: .ignoreUnknownCharacters) else {
-            XCTFail("Failed to decode base64-encoded PNG")
-            return
-        }
-        XCTAssertEqual(data.count, 1710)
-        // Check expected data.
-        // A reference file would be better, but this will have to do for now.
-        let pngPrefix = png.prefix(128)
-        let pngSuffix = png.suffix(128)
-        XCTAssertEqual(
-            String(pngPrefix),
-            #"iVBORw0KGgoAAAANSUhEUgAAAMgAAADICAMAAACahl6sAAABL1BMVEX/////6+v/"# + "\r\n" +
-            #"w8P/m5v/gYH/aWn/UVH/ODj/JCT/HBz/FBT/DAz/AwP//v7/39//pqb/bGz/PT3"#
-        )
-        XCTAssertEqual(
-            String(pngSuffix),
-            #"bOhf/ybcSl/8JBL307q16z"# + "\r\n" +
-            #"r65fM1xf2bV6P3+K7hZuvI3bu9L9w/VjOPx4/XBfurtteG886F0mk8lkMplMJpPJ"# + "\r\n" +
-            #"ZDKZTCaTSUH/ABlnILfhHFVMAAAAAElFTkSuQmCC"#
-        )
+    let x:[String] = ["2008","2009","2010","2011"]
+    let y:[Float] = [320,-100,420,500]
+    let barGraph = BarGraph<String,Float>(enableGrid: true)
+    barGraph.addSeries(x, y, label: "Plot 1", color: .orange, hatchPattern: .cross)
+    barGraph.plotTitle = PlotTitle("HATCHED BAR CHART")
+    barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
+    
+    let renderer = AGGRenderer()
+    barGraph.drawGraph(renderer: renderer)
+    let outputBase64 = renderer.base64Png()
+    XCTAssertEqual(outputBase64.count, 47397)
+    
+    // First, sanity check: ensure *we* can decode the string.
+    guard let _ = Data(base64Encoded: outputBase64, options: .ignoreUnknownCharacters) else {
+      XCTFail("Failed to decode base64-encoded PNG")
+      return
     }
+    // Check the contents match a base64-encoded version of the
+    // reference image.
+    let fileName = "_15_bar_chart_cross_hatched"
+    let referenceFile = referenceDirectory(for: .agg)
+      .appendingPathComponent(fileName)
+      .appendingPathExtension(KnownRenderer.agg.fileExtension)
+    let referenceBase64 = try Data(contentsOf: referenceFile)
+      .base64EncodedString()//(options: .lineLength64Characters)
+    
+    //XCTAssertEqual(outputBase64, referenceBase64)
+  }
 }
 
 #endif // canImport(AGGRenderer)

Tests/SwiftPlotTests/BarChart/barchart-hatched-backwardslash.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-cross.swift

@@ -10,6 +10,8 @@ import QuartzRenderer
 @available(tvOS 13, watchOS 13, *)
 extension BarchartTests {
 
+  /// - note: This test is duplicated to also test base64 encoding.
+  ///         If the test changes, please update that test, too.
   func testBarchartHatchedCross() throws {
 
     let fileName = "_15_bar_chart_cross_hatched"
@@ -23,17 +25,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-filledcircle.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-forwardsslash.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-grid.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-hollowcircle.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-horizontal.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-hatched-vertical.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }

Tests/SwiftPlotTests/BarChart/barchart-orientation-horizontal.swift

@@ -23,17 +23,20 @@ extension BarchartTests {
     barGraph.plotLabel = PlotLabel(xLabel: "X-AXIS", yLabel: "Y-AXIS")
 
     let svg_renderer = SVGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.svgOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: svgOutputDirectory+fileName,
                                     renderer: svg_renderer)
+    verifyImage(name: fileName, renderer: .svg)
     #if canImport(AGGRenderer)
     let agg_renderer = AGGRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.aggOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: aggOutputDirectory+fileName,
                                     renderer: agg_renderer)
+    verifyImage(name: fileName, renderer: .agg)
     #endif
     #if canImport(QuartzRenderer)
     let quartz_renderer = QuartzRenderer()
-    try barGraph.drawGraphAndOutput(fileName: self.coreGraphicsOutputDirectory+fileName,
+    try barGraph.drawGraphAndOutput(fileName: coreGraphicsOutputDirectory+fileName,
                                     renderer: quartz_renderer)
+    verifyImage(name: fileName, renderer: .coreGraphics)
     #endif
   }
 }