This library is a wrapper around Microsoft's PICT (Pairwise Independent Combinatorial Testing) tool, designed to work with Node.js for generating combinations of inputs for software testing. PICT is a powerful tool that helps reduce the number of tests needed while still ensuring comprehensive coverage by generating optimized combinations of inputs.

The library boasts excellent TypeScript support! 🪄

Before using this library, it's helpful to read Microsoft's official PICT documentation to learn about the tool and how it works.

npm install --save-dev pict-node

Imagine you have a function for creating order that accepts 6 parameters with several possible values for each argument.

This model has many possible combinations, which means we could have thousands of test cases to write and test. However, it's not practical to test all of them manually and in a reasonable amount of time. Instead, we can generate and test all possible pairs of values to achieve a good level of coverage.

import { pict } from "pict-node";

const model = [
  {
    key: "location",
    values: ["Poland", "Lithuania", "Germany", "USA"],
  },
  {
    key: "customer",
    values: ["Individuals", "Companies", "Partners"],
  },
  {
    key: "time",
    values: ["05:00", "11:99", "15:00", "21:30", "23:59"],
  },
  {
    key: "paymentSystem",
    values: ["VISA", "MasterCard", "PayPal", "WebMoney", "Qiwi"],
  },
  {
    key: "product",
    values: [
      {
        id: 1732,
      },
      {
        id: 319,
      },
      {
        id: 872,
      },
      {
        id: 650,
      },
    ],
  },
  {
    key: "discount",
    values: [true, false],
  },
];

const cases = await pict({ model });

PICT will generate the following test cases:

[
  // ... ... ...
  {
    location: "Lithuania",
    customer: "Individuals",
    time: "23:59",
    paymentSystem: "Qiwi",
    product: { id: 650 },
    discount: true,
  },
  {
    location: "USA",
    customer: "Partners",
    time: "05:00",
    paymentSystem: "VISA",
    product: { id: 319 },
    discount: false,
  },
  // ... ... ...
  {
    location: "Poland",
    customer: "Companies",
    time: "23:59",
    paymentSystem: "MasterCard",
    product: { id: 1732 },
    discount: true,
  },
  // ... ... ...
];

In most cases, to create test cases, you can use the pict function. The main feature of this function is that you can use any data type for the values.

import { pict } from "pict-node";
import { createOrder } from "./src";

// Define test model
const model = [
  {
    key: "country",
    values: ["USA", "Canada", "Germany"],
  },
  {
    key: "age",
    values: [10, 16, 18, 25, 70],
  },
  {
    key: "product",
    values: [{ id: 50 }, { id: 350 }],
  },
];

// Generate test cases
const cases = await pict({ model });

// Iterate test cases
for (const { country, age, product } of cases) {
  // Call a function with the current test case
  const result = createOrder({
    country,
    age,
    product,
  });

  // Verify that the function returns the expected result
  expect(result).toBe("The order has been created");
}

By default, pict-node generates a pair-wise test suite (all pairs covered), but the order can be set by option order to a value larger than two.

const cases = await pict(
  {
    model,
  },
  {
    order: 3,
  }
);

The library provides excellent support for TypeScript.

Here is an example of using this tool with TypeScript:

import { pict, alias, weight } from "pict-node";

const model = [
  {
    key: "amount",
    //                           ↓↓↓↓↓↓↓↓
    values: [1, alias([2, "two"] as const), 3],
  },
  {
    key: "fruit",
    //                       ↓↓↓↓↓↓↓↓
    values: [weight("Banana" as const, 10), "Orange", "Apple"],
  },
  // ↓↓↓↓↓
] as const;

const cases = await pict({ model });

The type of cases will be:

Array<{
  amount: 1 | 2 | "two" | 3;
  fruit: "Banana" | "Orange" | "Apple";
}>;

⚠️ Note that we use as const to get a literal types!**

Without as const the type of cases will be:

Array<{
  amount: number | string;
  fruit: string;
}>;

In practice, you might want to exclude some of the generated test cases because certain parameters can't exist together. You can use constraints and their powerful syntax for this.

Read PICT documentation to get more information about constraints.

Constraints are only applicable when using the strings function, which only accepts string values and provides additional options:

• aliasSeparator - the separator used for aliases (default: |)
• valueSeparator - the separator used for values (default: ,)
• negativePrefix - the prefix used for negative values (default: ~)
• caseSensitive - case sensitive (default: false)

⚠️ Be aware that the characters used for aliasSeparator, valueSeparator, and negativePrefix cannot be used in your values. If you must use them, you must replace them using the second argument (options).

import { strings } from "pict-node";

const model = [
  {
    key: "type",
    values: ["Primary", "Logical", "Single"],
  },
  {
    key: "size",
    values: ["10", "100", "500", "1000", "5000", "10000", "40000"],
  },
  {
    key: "fileSystem",
    values: ["FAT", "FAT32", "NTFS"],
  },
];

const constraints = [
  'IF [fileSystem] = "FAT"   THEN [Size] <= 4096;',
  'IF [fileSystem] = "FAT32" THEN [Size] <= 32000;',
];

const cases = await strings(
  {
    model,
    constraints,
  },
  {
    caseSensitive: true,
  }
);

If you need to use values of different types, you can use the pict function instead of the strings function. This way, you can specify any type you want for the values of your model.

Sub-models allow the bundling of certain parameters into groups that get their own combinatory orders. This can be useful if combinations of certain parameters need to be tested more thoroughly, or less thoroughly, or in separation from the other parameters in the model.

Read PICT documentation to get more information about sub-models.

Sub-models can be used with both the pict and strings API functions, and they are defined using the sub property.

import { pict } from "pict-node";

const model = [
  {
    key: "platform",
    values: ["x86", "x64", "arm"],
  },
  {
    key: "ram",
    values: [1, 4, 64],
  },
  {
    key: "os",
    values: ["Win7", "Win8", "Win10"],
  },
  {
    key: "browser",
    values: ["Edge", "Opera", "Chrome", "Firefox"],
  },
];

const sub = [
  {
    keys: ["os", "browser"],
    order: 2, // optional
  },
];

const cases = await pict({
  model,
  sub,
});

Seeding allows for specifying important e.g. regression-inducing combinations that should end up in any generated test suite.

Read PICT documentation to get more information about seeding.

Seeding can be used with both the pict and strings API functions, and they are defined using the seed property.

import { pict } from "pict-node";

const model = [
  {
    key: "platform",
    values: ["x86", "x64", "arm"],
  },
  {
    key: "ram",
    values: [1, 4, 64],
  },
  {
    key: "os",
    values: ["Win7", "Win8", "Win10"],
  },
  {
    key: "browser",
    values: ["Edge", "Opera", "Chrome", "Firefox"],
  },
];

const seed = [
  {
    ram: 64,
    browser: "Opera",
  },
  {
    ram: 64,
    os: "Win8",
    browser: "Firefox",
  },
];

const cases = await pict({
  model,
  seed,
});

Aliasing is a way of specifying multiple names for a single value. Multiple names do not change the combinatorial complexity of the model. No matter how many names a value has, they are treated as one entity. The only difference will be in the output; any test case that would normally have that one value will have one of its names instead. Names are rotated among the test cases.

Read PICT documentation to get more information about aliasing.

There is a special function alias that can be used to create aliases for values. It can be used with both the pict and strings API functions.

import { pict, alias } from "pict-node";

const model = [
  {
    key: "os",
    values: ["Win7", "Win8", alias(["Win10", "Windows10"])],
  },
  {
    key: "platform",
    values: ["x86", "x64", "arm"],
  },
  {
    key: "ram",
    values: [1, 4, 64],
  },
];

const cases = await pict({ model });

In addition to testing valid combinations, referred to as “positive testing,” it is often desirable to test using values outside the allowable range to make sure the program handles errors properly.

Read PICT documentation to get more information about negative testing.

There is a special function negative that can be used to create a value for negative testing. It can be used with both the pict and strings API functions.

import { pict, negative } from "pict-node";

const model = [
  {
    key: "A",
    values: [negative(-1), 0, 1, 2],
  },
  {
    key: "B",
    values: [negative(-1), 0, 1, 2],
  },
];

const cases = await pict({ model });

Weights tell the generator to prefer certain parameter values over others. Weights are positive integers. When not explicitly specified, values have a weight of 1:

Read PICT documentation to get more information about weighting.

There is a special function weight that can be used to create a value with weight. It can be used with both the pict and strings API functions.

import { pict, weight } from "pict-node";

const model = [
  {
    key: "type",
    values: [weight("Primary", 5), "Logical", "Single", "Span"],
  },
  {
    key: "formatMethod",
    values: ["quick", "slow"],
  },
  {
    key: "fileSystem",
    values: ["FAT", "FAT32", weight("NTFS", 10)],
  },
];

const cases = await pict({ model });

If a model and options given to the tool do not change, every run will result in the same output. However, the output can be randomized.

Read PICT documentation to get more information about randomization.

If the model does not change, running it repeatedly will result in the same output. To introduce randomness, you can use the random option.

It applies to pict, strings and native API.

import { pict } from "pict-node";

const model = [
  // ...
];

const cases = await pict(
  { model },
  {
    random: true,
    // random: 19285 - or using with seed
  }
);

You can use native PICT models with native API function.

native accepts the following options (optional):

• order - order of combinations (default: 2)
• random - randomization
• aliasSeparator - the separator used for aliases (default: |)
• valueSeparator - the separator used for values (default: ,)
• negativePrefix - the prefix used for negative values (default: ~)
• caseSensitive - case sensitive (default: false)

A model can be a file:

import { native } from "pict-node";

const cases = await native({
  model: {
    file: "path/to/file",
    seed: "path/to/seed/file", // optional,
    options: {
      caseSensitive: true,
    },
  },
});

A model and a seed can be a string:

import { native } from "pict-node";

const cases = await native({
  model: `
  PLATFORM:  x86, x64, arm
  RAM:       1GB, 4GB, 64GB
  OS:        Win7, Win8, Win10
  Browser:   Edge, Opera, Chrome, Firefox
  `,
});

You can obtain model statistics using the stats method.

This method is accessible through the pict, strings, and native APIs.

import { pict } from "pict-node";

const model = [
  {
    key: "platform",
    values: ["x86", "x64", "arm"],
  },
  {
    key: "ram",
    values: [1, 4, 64],
  },
];

const stats = await pict.stats({
  model,
});

The stats method returns an object with the following fields:

• generationTimeNodeJs - model generation time (including Node.js processing time)
• generationTime - model generation time (excluding Node.js processing time)
• combinations - number of combinations
• generatedTests - number of generated tests

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