From 0df6d5d18f5c33d6f45678de26eb0d7c9deb290c Mon Sep 17 00:00:00 2001
From: Lee Nipper <lee.nipper@gmail.com>
Date: Sat, 18 Nov 2017 16:20:09 -0600
Subject: [PATCH] nth-prime: add generator

Add .meta/gen.go to generate cases_test.go.

Update test program to use generated test case array.
Output FAIL and PASS in test output.

For #605.
---
 exercises/nth-prime/.meta/gen.go      | 76 +++++++++++++++++++++++++++
 exercises/nth-prime/cases_test.go     | 43 +++++++++++++++
 exercises/nth-prime/nth_prime_test.go | 22 ++------
 3 files changed, 123 insertions(+), 18 deletions(-)
 create mode 100644 exercises/nth-prime/.meta/gen.go
 create mode 100644 exercises/nth-prime/cases_test.go

diff --git a/exercises/nth-prime/.meta/gen.go b/exercises/nth-prime/.meta/gen.go
new file mode 100644
index 000000000..84846c75e
--- /dev/null
+++ b/exercises/nth-prime/.meta/gen.go
@@ -0,0 +1,76 @@
+package main
+
+import (
+	"log"
+	"text/template"
+
+	"../../../gen"
+)
+
+func main() {
+	t, err := template.New("").Parse(tmpl)
+	if err != nil {
+		log.Fatal(err)
+	}
+	var j js
+	if err := gen.Gen("nth-prime", &j, t); err != nil {
+		log.Fatal(err)
+	}
+}
+
+type OneCase struct {
+	Description string
+	Input       int
+	Expected    interface{}
+}
+
+// The JSON structure we expect to be able to unmarshal into
+type js struct {
+	Cases []OneCase
+}
+
+func (c OneCase) HasPrimeAnswer() bool {
+	hasPrimeAnswer, _ := determineExpected(c.Expected)
+	return hasPrimeAnswer
+}
+
+func (c OneCase) PrimeAnswer() int {
+	_, answer := determineExpected(c.Expected)
+	return answer
+}
+
+// determineExpected examines an .Expected interface{} object and determines
+// whether a test case has a Prime answer or expects an error,
+// returning true and the answer, or false and zero.
+func determineExpected(expected interface{}) (bool, int) {
+	value, ok := expected.(float64)
+	if ok {
+		return true, int(value)
+	}
+	return false, 0
+}
+
+// template applied to above data structure generates the Go test cases
+var tmpl = `package prime
+
+{{.Header}}
+
+var tests = []struct {
+	description string
+	n   int
+	p   int
+	ok  bool
+}{
+{{range .J.Cases}}{
+	"{{.Description}}",
+	{{.Input}},
+{{- if .HasPrimeAnswer}}
+	{{.PrimeAnswer}},
+	true,
+{{- else}}
+	0,
+	false,
+{{- end}}
+},
+{{end}}}
+`
diff --git a/exercises/nth-prime/cases_test.go b/exercises/nth-prime/cases_test.go
new file mode 100644
index 000000000..d93db3ce0
--- /dev/null
+++ b/exercises/nth-prime/cases_test.go
@@ -0,0 +1,43 @@
+package prime
+
+// Source: exercism/problem-specifications
+// Commit: e82cbcd nth-prime: Use object instead of bool for invalid value (#969)
+// Problem Specifications Version: 2.0.0
+
+var tests = []struct {
+	description string
+	n           int
+	p           int
+	ok          bool
+}{
+	{
+		"first prime",
+		1,
+		2,
+		true,
+	},
+	{
+		"second prime",
+		2,
+		3,
+		true,
+	},
+	{
+		"sixth prime",
+		6,
+		13,
+		true,
+	},
+	{
+		"big prime",
+		10001,
+		104743,
+		true,
+	},
+	{
+		"there is no zeroth prime",
+		0,
+		0,
+		false,
+	},
+}
diff --git a/exercises/nth-prime/nth_prime_test.go b/exercises/nth-prime/nth_prime_test.go
index 03f23e807..a828a5a0b 100644
--- a/exercises/nth-prime/nth_prime_test.go
+++ b/exercises/nth-prime/nth_prime_test.go
@@ -2,33 +2,19 @@ package prime
 
 import "testing"
 
-var tests = []struct {
-	n  int
-	p  int
-	ok bool
-}{
-	{1, 2, true},
-	{2, 3, true},
-	{3, 5, true},
-	{4, 7, true},
-	{5, 11, true},
-	{6, 13, true},
-	{10001, 104743, true},
-	{0, 0, false},
-}
-
 func TestNth(t *testing.T) {
 	for _, test := range tests {
 		switch p, ok := Nth(test.n); {
 		case !ok:
 			if test.ok {
-				t.Fatalf("Nth(%d) returned !ok.  Expecting ok.", test.n)
+				t.Fatalf("FAIL %s\nNth(%d) returned !ok.  Expecting ok.", test.description, test.n)
 			}
 		case !test.ok:
-			t.Fatalf("Nth(%d) = %d, ok = %t.  Expecting !ok.", test.n, p, ok)
+			t.Fatalf("FAIL %s\nNth(%d) = %d, ok = %t.  Expecting !ok.", test.description, test.n, p, ok)
 		case p != test.p:
-			t.Fatalf("Nth(%d) = %d, want %d.", test.n, p, test.p)
+			t.Fatalf("FAIL %s\nNth(%d) = %d, want %d.", test.description, test.n, p, test.p)
 		}
+		t.Logf("PASS %s", test.description)
 	}
 }