Adding tests from Deneb Showcase repo

.gitignore

@@ -1,5 +1,6 @@
-*.svg
-*.js
+/candlestick.svg
+/layer-line.svg
+
 *.png
 *.jpg
 *.txt

source.go

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+package vegagoja
+
+import (
+	"io/fs"
+	"os"
+	"strings"
+)
+
+// Source is a cascading [fs.FS] implementation.
+type Source struct {
+	sources []fs.FS
+}
+
+// NewSource creates a source data source for the supplied file systems.
+func NewSource(sources ...fs.FS) fs.FS {
+	if len(sources) == 1 {
+		return sources[0]
+	}
+	return &Source{
+		sources: sources,
+	}
+}
+
+// Open satisfies the [fs.FS] interface.
+func (s *Source) Open(name string) (fs.File, error) {
+	for _, source := range s.sources {
+		if file, err := source.Open(name); err == nil {
+			return file, nil
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+// PrefixedSource is a prefixed source.
+type PrefixedSource struct {
+	prefix string
+	source fs.FS
+}
+
+// NewPrefixedSource creates a prefixed source.
+func NewPrefixedSource(prefix string, source fs.FS) *PrefixedSource {
+	return &PrefixedSource{
+		prefix: prefix,
+		source: source,
+	}
+}
+
+// NewPrefixedSourceDir creates a prefixed source for the specified directory.
+func NewPrefixedSourceDir(prefix, dir string) *PrefixedSource {
+	return &PrefixedSource{
+		prefix: prefix,
+		source: os.DirFS(dir),
+	}
+}
+
+// Open satisfies the [fs.FS] interface.
+func (s *PrefixedSource) Open(name string) (fs.File, error) {
+	if !strings.HasPrefix(name, s.prefix) {
+		return nil, os.ErrNotExist
+	}
+	return s.source.Open(strings.TrimPrefix(name, s.prefix))
+}
+
+// ResultSet is the shared interface for a result set.
+type ResultSet interface {
+	Next() bool
+	Scan(...interface{}) error
+	Columns() ([]string, error)
+	Close() error
+	Err() error
+	NextResultSet() bool
+}

testdata/deneb/LICENSE

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+MIT License
+
+Copyright (c) 2023 Davide Bacci
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

testdata/deneb/README.md

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+# About
+
+The examples in this folder are taken from [David Bacci's][david-bacci-linkedin]
+[Deneb Showcase][deneb-showcase], and modified under the [MIT License](./LICENSE).
+
+[david-bacci-linkedin]: https://www.linkedin.com/in/davbacci/
+[deneb-showcase]: https://github.com/PBI-David/Deneb-Showcase