Upgrade to Gatsby v2

tests/__mocks__/fileMock.js

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+'use strict';
+
+module.exports = 'file';

tests/__mocks__/gatsby.js

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+'use strict';
+
+const gatsby = jest.requireActual('gatsby');
+
+module.exports = {
+  ...gatsby,
+  graphql: jest.fn(),
+  Link: 'Link',
+  StaticQuery: 'StaticQuery'
+};

tests/jest-config.js

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+'use strict';
+
+module.exports = {
+  rootDir: '../',
+  transform: {
+    '^.+\\.js?$': '<rootDir>/tests/jest-preprocess.js'
+  },
+  testMatch: ['**/__tests__/**/*.js', '**/?(*.)test.js'],
+  moduleNameMapper: {
+    '.+\\.(css|styl|less|sass|scss)$': 'identity-obj-proxy',
+    '.+\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$': '<rootDir>/tests/__mocks__/fileMock.js'
+  },
+  testPathIgnorePatterns: ['node_modules', '.cache', 'public'],
+  transformIgnorePatterns: [
+    'node_modules/(?!(gatsby)/)'
+  ],
+  globals: {
+    __PATH_PREFIX__: ''
+  },
+  testURL: 'http://localhost/'
+};

tests/jest-preprocess.js

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+'use strict';
+
+const babelOptions = {
+  presets: ['@babel/react', '@babel/env'],
+  plugins: [
+    '@babel/plugin-proposal-optional-chaining',
+    '@babel/plugin-proposal-class-properties'
+  ],
+};
+
+module.exports = require('babel-jest').createTransformer(babelOptions);