github.com/leanovate/gopter@v0.2.9/prop/example_quadratic_test.go (about)

     1  package prop_test
     2  
     3  import (
     4  	"errors"
     5  	"math"
     6  
     7  	"github.com/leanovate/gopter"
     8  	"github.com/leanovate/gopter/gen"
     9  	"github.com/leanovate/gopter/prop"
    10  )
    11  
    12  func solveQuadratic(a, b, c float64) (float64, float64, error) {
    13  	if a == 0 {
    14  		return 0, 0, errors.New("No solution")
    15  	}
    16  	v := b*b - 4*a*c
    17  	if v < 0 {
    18  		return 0, 0, errors.New("No solution")
    19  	}
    20  	v = math.Sqrt(v)
    21  	return (-b + v) / 2 / a, (-b - v) / 2 / a, nil
    22  }
    23  
    24  func Example_quadratic() {
    25  	parameters := gopter.DefaultTestParametersWithSeed(1234) // Example should generate reproducible results, otherwise DefaultTestParameters() will suffice
    26  
    27  	properties := gopter.NewProperties(parameters)
    28  
    29  	properties.Property("solve quadratic", prop.ForAll(
    30  		func(a, b, c float64) bool {
    31  			x1, x2, err := solveQuadratic(a, b, c)
    32  			if err != nil {
    33  				return true
    34  			}
    35  			return math.Abs(a*x1*x1+b*x1+c) < 1e-5 && math.Abs(a*x2*x2+b*x2+c) < 1e-5
    36  		},
    37  		gen.Float64(),
    38  		gen.Float64(),
    39  		gen.Float64(),
    40  	))
    41  
    42  	properties.Property("solve quadratic with resonable ranges", prop.ForAll(
    43  		func(a, b, c float64) bool {
    44  			x1, x2, err := solveQuadratic(a, b, c)
    45  			if err != nil {
    46  				return true
    47  			}
    48  			return math.Abs(a*x1*x1+b*x1+c) < 1e-5 && math.Abs(a*x2*x2+b*x2+c) < 1e-5
    49  		},
    50  		gen.Float64Range(-1e8, 1e8),
    51  		gen.Float64Range(-1e8, 1e8),
    52  		gen.Float64Range(-1e8, 1e8),
    53  	))
    54  
    55  	// When using testing.T you might just use: properties.TestingRun(t)
    56  	properties.Run(gopter.ConsoleReporter(false))
    57  	// Output:
    58  	// ! solve quadratic: Falsified after 0 passed tests.
    59  	// ARG_0: -1.4667384313385178e-05
    60  	// ARG_0_ORIGINAL (187 shrinks): -1.0960555181801604e+51
    61  	// ARG_1: 0
    62  	// ARG_1_ORIGINAL (1 shrinks): -1.1203884793568249e+96
    63  	// ARG_2: 6.481285637227244e+10
    64  	// ARG_2_ORIGINAL (905 shrinks): 1.512647219322138e+281
    65  	// + solve quadratic with resonable ranges: OK, passed 100 tests.
    66  }