github.com/stretchr/testify v1.7.0: assert.InEpsilon

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pkg:golang/github.com/stretchr/testify@v1.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/stretchr/testify@v1.7.0
Demonstrate these symbols/APIs:
  - github.com/stretchr/testify/assert.InEpsilon

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:51830139d601a7d270061013340b31e414f45c4b7249f8b214cdce6dafda908a","contract":["assert.InEpsilon returns true and records no error when relative error between expected and actual is within epsilon","assert.InEpsilon returns false and records an error when relative error exceeds epsilon","assert.InEpsilon returns false and records an error when expected is zero because relative error requires non-zero expected","assert.InEpsilon converts integer and float types to float64 to calculate relative error","assert.InEpsilon returns false and records an error when expected or actual is non-numeric or NaN","assert.InEpsilon returns false and records an error when epsilon is NaN","assert.InEpsilon formats and includes custom message arguments when an assertion fails"],"goal":"verify pkg:golang/github.com/stretchr/testify@v1.7.0","kind":"HOW","packages":["pkg:golang/github.com/stretchr/testify@v1.7.0"],"schemaVersion":1,"symbols":["github.com/stretchr/testify/assert.InEpsilon"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/stretchr/testify@v1.7.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/stretchr/testify@v1.7.0","symbols":["github.com/stretchr/testify/assert.InEpsilon"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/stretchr/testify v1.7.0

require (
	github.com/davecgh/go-spew v1.1.0 // indirect
	github.com/pmezard/go-difflib v1.0.0 // indirect
	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
)

github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"fmt"

	"github.com/stretchr/testify/assert"
)

type OutputCapture struct {
	errors []string
	failed bool
}

func (c *OutputCapture) Errorf(format string, args ...interface{}) {
	c.failed = true
	c.errors = append(c.errors, fmt.Sprintf(format, args...))
}

func main() {
	capture := &OutputCapture{}

	// Example 1: Verify floating-point calculation within 1% relative tolerance
	expectedRate := 100.0
	actualRate := 100.5
	epsilon := 0.01 // 1% tolerance

	if assert.InEpsilon(capture, expectedRate, actualRate, epsilon, "transfer rate should be within tolerance") {
		fmt.Printf("Rate verified within %.1f%% relative tolerance: %.2f vs %.2f\n", epsilon*100, actualRate, expectedRate)
	}

	// Example 2: Verify mixed numeric types (int vs float64)
	expectedCount := 500
	actualCount := 502.0
	if assert.InEpsilon(capture, expectedCount, actualCount, 0.01, "item count should match expected pace") {
		fmt.Println("Mixed integer and float pace verified within relative epsilon.")
	}

	if !capture.failed {
		fmt.Println("All testify assert.InEpsilon demonstrations completed successfully.")
	}
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/stretchr/testify@v1.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/stretchr/testify@v1.7.0"
  ],
  "symbols": [
    "github.com/stretchr/testify/assert.InEpsilon"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"
	"strings"

	"github.com/stretchr/testify/assert"
)

type contractTestingT struct {
	errors []string
	failed bool
}

func (t *contractTestingT) Errorf(format string, args ...interface{}) {
	t.failed = true
	t.errors = append(t.errors, fmt.Sprintf(format, args...))
}

func main() {
	// Assertion 1: assert.InEpsilon returns true and records no error when relative error between expected and actual is within epsilon
	{
		t := &contractTestingT{}
		expected := 100.0
		actual := 100.5
		epsilon := 0.01 // relative diff = 0.5 / 100.0 = 0.005 <= 0.01
		if !assert.InEpsilon(t, expected, actual, epsilon) || t.failed || len(t.errors) != 0 {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: InEpsilon should succeed when relative error is within epsilon\n")
			os.Exit(1)
		}
	}

	// Assertion 2: assert.InEpsilon returns false and records an error when relative error exceeds epsilon
	{
		t := &contractTestingT{}
		expected := 100.0
		actual := 102.0
		epsilon := 0.01 // relative diff = 2.0 / 100.0 = 0.02 > 0.01
		if assert.InEpsilon(t, expected, actual, epsilon) || !t.failed || len(t.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: InEpsilon should fail when relative error exceeds epsilon\n")
			os.Exit(1)
		}
	}

	// Assertion 3: assert.InEpsilon returns false and records an error when expected is zero because relative error requires non-zero expected
	{
		tZero := &contractTestingT{}
		if assert.InEpsilon(tZero, 0.0, 0.005, 0.01) || !tZero.failed || len(tZero.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: InEpsilon should fail when expected is zero\n")
			os.Exit(1)
		}
	}

	// Assertion 4: assert.InEpsilon converts integer and float types to float64 to calculate relative error
	{
		t := &contractTestingT{}
		expectedInt := 50
		actualFloat := 50.1
		epsilon := 0.01
		if !assert.InEpsilon(t, expectedInt, actualFloat, epsilon) || t.failed || len(t.errors) != 0 {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: InEpsilon should succeed comparing mixed int and float types\n")
			os.Exit(1)
		}
	}

	// Assertion 5: assert.InEpsilon returns false and records an error when expected or actual is non-numeric or NaN
	{
		tNonNumeric := &contractTestingT{}
		if assert.InEpsilon(tNonNumeric, "not-a-number", 1.0, 0.01) || !tNonNumeric.failed || len(tNonNumeric.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: InEpsilon should fail on non-numeric parameter\n")
			os.Exit(1)
		}

		tNaN := &contractTestingT{}
		if assert.InEpsilon(tNaN, math.NaN(), 1.0, 0.01) || !tNaN.failed || len(tNaN.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: InEpsilon should fail when expected is NaN\n")
			os.Exit(1)
		}
	}

	// Assertion 6: assert.InEpsilon returns false and records an error when epsilon is NaN
	{
		tEpsNaN := &contractTestingT{}
		if assert.InEpsilon(tEpsNaN, 100.0, 100.1, math.NaN()) || !tEpsNaN.failed || len(tEpsNaN.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 6 failed: InEpsilon should fail when epsilon is NaN\n")
			os.Exit(1)
		}
	}

	// Assertion 7: assert.InEpsilon formats and includes custom message arguments when an assertion fails
	{
		tMsg := &contractTestingT{}
		assert.InEpsilon(tMsg, 100.0, 200.0, 0.01, "tolerance exceeded for run %d", 42)
		if !tMsg.failed || len(tMsg.errors) == 0 {
			fmt.Fprintf(os.Stderr, "assertion 7 failed: expected failure on InEpsilon\n")
			os.Exit(1)
		}
		if !strings.Contains(tMsg.errors[0], "tolerance exceeded for run 42") {
			fmt.Fprintf(os.Stderr, "assertion 7 failed: custom message not formatted in InEpsilon: %s\n", tMsg.errors[0])
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed successfully.")
}