export format property variables (#347)

* export format property variables

* add test with different length diffs

* add test with different diff threshold

* use uint for exported parameters

* use BDD style descriptions

* test extremes of config

format/format.go

@@ -36,6 +36,14 @@ var PrintContextObjects = false
 // TruncatedDiff choose if we should display a truncated pretty diff or not
 var TruncatedDiff = true
 
+// TruncateThreshold (default 50) specifies the maximum length string to print in string comparison assertion error
+// messages.
+var TruncateThreshold uint = 50
+
+// CharactersAroundMismatchToInclude (default 5) specifies how many contextual characters should be printed before and
+// after the first diff location in a truncated string assertion error message.
+var CharactersAroundMismatchToInclude uint = 5
+
 // Ctx interface defined here to keep backwards compatibility with go < 1.7
 // It matches the context.Context interface
 type Ctx interface {
@@ -88,7 +96,7 @@ to equal               |
 */
 
 func MessageWithDiff(actual, message, expected string) string {
-	if TruncatedDiff && len(actual) >= truncateThreshold && len(expected) >= truncateThreshold {
+	if TruncatedDiff && len(actual) >= int(TruncateThreshold) && len(expected) >= int(TruncateThreshold) {
 		diffPoint := findFirstMismatch(actual, expected)
 		formattedActual := truncateAndFormat(actual, diffPoint)
 		formattedExpected := truncateAndFormat(expected, diffPoint)
@@ -116,15 +124,15 @@ func truncateAndFormat(str string, index int) string {
 	leftPadding := `...`
 	rightPadding := `...`
 
-	start := index - charactersAroundMismatchToInclude
+	start := index - int(CharactersAroundMismatchToInclude)
 	if start < 0 {
 		start = 0
 		leftPadding = ""
 	}
 
 	// slice index must include the mis-matched character
 	lengthOfMismatchedCharacter := 1
-	end := index + charactersAroundMismatchToInclude + lengthOfMismatchedCharacter
+	end := index + int(CharactersAroundMismatchToInclude) + lengthOfMismatchedCharacter
 	if end > len(str) {
 		end = len(str)
 		rightPadding = ""
@@ -153,11 +161,6 @@ func findFirstMismatch(a, b string) int {
 	return 0
 }
 
-const (
-	truncateThreshold                 = 50
-	charactersAroundMismatchToInclude = 5
-)
-
 /*
 Pretty prints the passed in object at the passed in indentation level.
 

format/format_test.go

@@ -190,6 +190,99 @@ var _ = Describe("Format", func() {
 				Expect(MessageWithDiff(stringWithB, "to equal", stringWithZ)).Should(Equal(expectedFullFailureDiff))
 			})
 		})
+
+		Context("With alternate diff lengths", func() {
+			initialValue := TruncateThreshold // 50 by default
+			BeforeEach(func() {
+				TruncateThreshold = 10000
+			})
+
+			AfterEach(func() {
+				TruncateThreshold = initialValue
+			})
+
+			It("should show the full diff when truncate threshold is increased beyond length of strings", func() {
+				stringWithB := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+				stringWithZ := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaazaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+				Expect(MessageWithDiff(stringWithB, "to equal", stringWithZ)).Should(Equal(expectedFullFailureDiff))
+			})
+		})
+
+		Context("with alternative number of characters to include around mismatch", func() {
+			initialValue := CharactersAroundMismatchToInclude // 5 by default
+			BeforeEach(func() {
+				CharactersAroundMismatchToInclude = 10
+			})
+
+			AfterEach(func() {
+				CharactersAroundMismatchToInclude = initialValue
+			})
+
+			It("it shows more characters around a line length mismatch", func() {
+				smallString := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+				largeString := "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+
+				Expect(MessageWithDiff(largeString, "to equal", smallString)).Should(Equal(expectedTruncatedStartSizeFailureMessageExtraDiff))
+				Expect(MessageWithDiff(smallString, "to equal", largeString)).Should(Equal(expectedTruncatedStartSizeSwappedFailureMessageExtraDiff))
+			})
+		})
+
+		Describe("At extremes of configurable values", func() {
+			Context("with zero-length threshold", func() {
+				initialValue := TruncateThreshold // 50 by default
+				BeforeEach(func() {
+					TruncateThreshold = 0
+				})
+
+				AfterEach(func() {
+					TruncateThreshold = initialValue
+				})
+
+				It("should show the full diff when truncate threshold is increased beyond length of strings", func() {
+					stringWithB := "aba"
+					stringWithZ := "aza"
+					Expect(MessageWithDiff(stringWithB, "to equal", stringWithZ)).Should(Equal(expectedDiffSmallThreshold))
+				})
+			})
+
+			Context("with zero characters around mismatch", func() {
+				initialValue := CharactersAroundMismatchToInclude // 5 by default
+				BeforeEach(func() {
+					CharactersAroundMismatchToInclude = 0
+				})
+
+				AfterEach(func() {
+					CharactersAroundMismatchToInclude = initialValue
+				})
+
+				It("", func() {
+					stringWithB := "aba"
+					stringWithZ := "aza"
+					Expect(MessageWithDiff(stringWithB, "to equal", stringWithZ)).Should(Equal(expectedDiffZeroMismatch))
+				})
+			})
+
+			Context("with zero-length threshold and zero characters around mismatch", func() {
+				initialCharactersAroundMismatch := CharactersAroundMismatchToInclude
+				initialTruncateThreshold := TruncateThreshold
+				BeforeEach(func() {
+					CharactersAroundMismatchToInclude = 0
+					TruncateThreshold = 0
+				})
+
+				AfterEach(func() {
+					CharactersAroundMismatchToInclude = initialCharactersAroundMismatch
+					TruncateThreshold = initialTruncateThreshold
+				})
+
+				It("", func() {
+					stringWithB := "aba"
+					stringWithZ := "aza"
+					Expect(MessageWithDiff(stringWithB, "to equal", stringWithZ)).Should(Equal(expectedDiffSmallThresholdZeroMismatch))
+				})
+			})
+		})
 	})
 
 	Describe("IndentString", func() {
@@ -613,30 +706,58 @@ Expected
 to equal               |
     <string>: "...aaaaa"
 `)
+var expectedTruncatedStartSizeFailureMessageExtraDiff = strings.TrimSpace(`
+Expected
+    <string>: "...aaaaaaaaaaa"
+to equal                    |
+    <string>: "...aaaaaaaaaa"
+`)
 var expectedTruncatedStartSizeSwappedFailureMessage = strings.TrimSpace(`
 Expected
     <string>: "...aaaa"
 to equal              |
     <string>: "...aaaaa"
 `)
+var expectedTruncatedStartSizeSwappedFailureMessageExtraDiff = strings.TrimSpace(`
+Expected
+    <string>: "...aaaaaaaaa"
+to equal                   |
+    <string>: "...aaaaaaaaaa"
+`)
 var expectedTruncatedMultiByteFailureMessage = strings.TrimSpace(`
 Expected
     <string>: "...tuvwxyz1"
 to equal                 |
     <string>: "...tuvwxyz"
 `)
-
 var expectedFullFailureDiff = strings.TrimSpace(`
 Expected
     <string>: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 to equal
     <string>: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaazaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 `)
-
 var expectedSpecialCharacterFailureMessage = strings.TrimSpace(`
 Expected
     <string>: \n
 to equal
     <string>: something_else
 
 `)
+var expectedDiffSmallThreshold = strings.TrimSpace(`
+Expected
+    <string>: "aba"
+to equal        |
+    <string>: "aza"
+`)
+var expectedDiffZeroMismatch = strings.TrimSpace(`
+Expected
+    <string>: aba
+to equal
+    <string>: aza
+`)
+var expectedDiffSmallThresholdZeroMismatch = strings.TrimSpace(`
+Expected
+    <string>: "...b..."
+to equal          |
+    <string>: "...z..."
+`)