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Hypothesis strategies for GraphQL queries and mutations

Project description

hypothesis-graphql

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Hypothesis strategies for GraphQL operations. Allows you to generate arbitrary GraphQL queries for the given schema. It starts with simple examples and iteratively goes to more complex ones.

For web API testing, Schemathesis provides a higher-level wrapper and can detect internal server errors.

Usage

hypothesis_graphql exposes the from_schema function, which takes a GraphQL schema and returns a Hypothesis strategy for defined queries and mutations:

from hypothesis import given
from hypothesis_graphql import from_schema

SCHEMA = """
type Book {
  title: String
  author: Author
}

type Author {
  name: String
  books: [Book]
}

type Query {
  getBooks: [Book]
  getAuthors: [Author]
}

type Mutation {
  addBook(title: String!, author: String!): Book!
  addAuthor(name: String!): Author!
}
"""


@given(from_schema(SCHEMA))
def test_graphql(query):
    # Will generate samples like these:
    #
    # {
    #   getBooks {
    #     title
    #   }
    # }
    #
    # mutation {
    #   addBook(title: "H4Z\u7869", author: "\u00d2"){
    #     title
    #   }
    # }
    ...

It is also possible to generate queries or mutations separately with hypothesis_graphql.queries and hypothesis_graphql.mutations.

Customization

To restrict the set of fields in generated operations use the fields argument:

@given(from_schema(SCHEMA, fields=["getAuthors"]))
def test_graphql(query):
    # Only `getAuthors` will be generated
    ...

It is also possible to generate custom scalars. For example, Date:

from hypothesis import strategies as st, given
from hypothesis_graphql import from_schema, nodes

SCHEMA = """
scalar Date

type Query {
  getByDate(created: Date!): Int
}
"""


@given(
    from_schema(
        SCHEMA,
        custom_scalars={
            # Standard scalars work out of the box, for custom ones you need
            # to pass custom strategies that generate proper AST nodes
            "Date": st.dates().map(nodes.String)
        },
    )
)
def test_graphql(query):
    # Example:
    #
    #  { getByDate(created: "2000-01-01") }
    #
    ...

The hypothesis_graphql.nodes module includes a few helpers to generate various node types:

  • String -> graphql.StringValueNode
  • Float -> graphql.FloatValueNode
  • Int -> graphql.IntValueNode
  • Object -> graphql.ObjectValueNode
  • List -> graphql.ListValueNode
  • Boolean -> graphql.BooleanValueNode
  • Enum -> graphql.EnumValueNode
  • Null -> graphql.NullValueNode (a constant, not a function)

They exist because classes like graphql.StringValueNode can't be directly used in map calls due to kwarg-only arguments.

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