Fix graphviz_test with test table

The tests were explicitly checking order where the underlying implementation is `map[string]*BasicNode`. This PR addresses the order which is not known and within the test I create a test table to allow multiple tests (2 in this PR rather than 1).

digraph/graphviz_test.go

@@ -1,44 +1,101 @@
 package digraph
 
 import (
-	"bytes"
-	"strings"
-	"testing"
+  "bytes"
+  "reflect"
+  "sort"
+  "strings"
+  "testing"
 )
 
+var testTable = []struct {
+  BasicData           string // Basic graph data
+  ExpectedDigraphData string // Digraph data which should be generated from BasicData
+}{
+  {
+    `a -> b ; foo
+     a -> c
+     b -> d
+     b -> e
+    `,
+    `digraph {
+     "a";
+     "a" -> "b" [label="foo"];
+     "a" -> "c" [label="Edge"];
+     "b";
+     "b" -> "d" [label="Edge"];
+     "b" -> "e" [label="Edge"];
+     "c";
+     "d";
+     "e";
+    }`,
+  },
+  {
+    `a -> c ; foo
+     a -> d
+     b -> c
+     b -> e
+     a -> f
+    `,
+    `digraph {
+     "a";
+     "a" -> "c" [label="foo"];
+     "a" -> "f" [label="Edge"];
+     "a" -> "d" [label="Edge"];
+     "b";
+     "b" -> "c" [label="Edge"];
+     "b" -> "e" [label="Edge"];
+     "c";
+     "d";
+     "e";
+     "f";
+    }`,
+  },
+}
+
+// Nieve normalizer. Takes a string, splits it and sorts it.
+func normalize(input string) []string {
+  out := strings.Split(input, "\n")
+
+  // trim each line
+  for i, str := range out {
+    out[i] = strings.TrimSpace(str)
+  }
+
+  sort.Strings(out)
+  return out
+}
+
 func TestWriteDot(t *testing.T) {
-	nodes := ParseBasic(`a -> b ; foo
-a -> c
-b -> d
-b -> e
-`)
-	var nlist []Node
-	for _, n := range nodes {
-		nlist = append(nlist, n)
-	}
+  // Build []Node from BasicNode map
+  var buildNodes = func(nodes map[string]*BasicNode) []Node {
+    var nlist []Node
+    for _, n := range nodes {
+      nlist = append(nlist, n)
+    }
+    return nlist
+  }
 
-	buf := bytes.NewBuffer(nil)
-	if err := WriteDot(buf, nlist); err != nil {
-		t.Fatalf("err: %s", err)
-	}
+  // Get a normalized string representation of the file
+  var writeFile = func(nlist []Node) string {
+    buf := bytes.NewBuffer(nil)
+    if err := WriteDot(buf, nlist); err != nil {
+      t.Fatalf("err: %s", err)
+    }
+    return strings.TrimSpace(string(buf.Bytes()))
+  }
 
-	actual := strings.TrimSpace(string(buf.Bytes()))
-	expected := strings.TrimSpace(writeDotStr)
-	if actual != expected {
-		t.Fatalf("bad: %s", actual)
-	}
+  // For each entry in the test table construct an
+  // actual and expected values and compare.
+  for _, data := range testTable {
+    nodes := buildNodes(ParseBasic(data.BasicData))
+    actual := normalize(writeFile(nodes))
+    expected := normalize(strings.TrimSpace(data.ExpectedDigraphData))
+
+    // Deep equal the array values
+    if !reflect.DeepEqual(actual, expected) {
+      t.Logf("Expected:\n%s", expected)
+      t.Fatalf("Bad:\n%s", actual)
+    }
+  }
 }
-
-const writeDotStr = `
-digraph {
-	"a";
-	"a" -> "b" [label="foo"];
-	"a" -> "c" [label="Edge"];
-	"b";
-	"b" -> "d" [label="Edge"];
-	"b" -> "e" [label="Edge"];
-	"c";
-	"d";
-	"e";
-}
-`