#### osnap

Random snapshot testing library for OCaml.

The Documentation can be found here. This library

uses QCheck generators to generate random values

for snapshots.

### Build

Build from source:

```
$ git clone git@github.com:vch9/osnap.git
$ dune build
```

You can also install with opam:

```
$ opam install osnap
```

### License

The code is now released under the MIT license.

### An introduction to the library

The library intends to test differences on results between two versions.

#### Binary Exponentiation

Let's say we write a function computing the exponentiation.

```
let rec exponentiation x n =
if n = 0 then 1
else if n = 1 then x
else exponentiation x (n - 1) * x
let test =
let open Osnap in
let spec = Spec.(small_int ^> small_int ^>> string_of_int) in
let path = ".osnap/exponentiation" in
Test.make ~spec ~path ~count:5 ~name:"exponentiation" exponentiation
let _ =
Osnap.Runner.(run_tests ~mode:Interactive [ test ])
```

In the above, we first provide a naive implementation of the exponentiation.

Then, we create a test with the according specification using `Osnap`

combinator.

```
{
name = exponentiation;
scenarios = [
35 66 = 4292184014870020553
0 3 = 0
9 3 = 729
3 7 = 2187
67 9 = 27206534396294947
]
}
Do you want to promote these diff? [Y\n]
```

As we agree with our function result, we promote the change by typing `Y`

.

We try to improve our function efficiency with binary exponentiation.

```
let rec binary_expo x n =
if n = 0 then 1
else if n mod 2 = 0 then
let tmp = binary_expo x (n / 2) in
tmp * tmp
else x * binary_expo x (n - 1)
let test =
let open Osnap in
let spec = Spec.(small_int ^> small_int ^>> string_of_int) in
let path = ".osnap/exponentiation" in
Test.make ~spec ~path ~count:5 ~name:"exponentiation" binary_expo
let _ = Osnap.Runner.(run_tests ~mode:Interactive [ test ])
```

Finally, we get the following result:

```
-------------------------------------------------------------------------------
success: ran 1 test (1 passed)
```

`Osnap`

has not found any difference between the old and new snapshot :heavy_check_mark:.

md5=2682db989c9b3143230d58ef027e5bf1

sha512=ffea89af2280470d1a6581e75ea7be7520d4a2726bd07ea00532b82709048df389776d2b3be1f96e3cd11412f81d9ec8d50c6babc5a86355f0cd2a2bae44b642

dev & >= "2.5.0"

with-doc

with-test & = "0.17"

>= "0.17"

>= "0.4"

>= "5.2.1"

>= "4.12.0"

>= "2.8.0"