start echidna tests and add to workflow

.github/workflows/fuzz-testing.yml

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+name: Fuzz Testing
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  echidna:
+    name: Echidna
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        testName:
+          - TickBitmapEchidnaTest
+          - TickMathEchidnaTest
+          - SqrtPriceMathEchidnaTest
+          - SwapMathEchidnaTest
+          - TickEchidnaTest
+          - TickOverflowSafetyEchidnaTest
+          - OracleEchidnaTest
+          - BitMathEchidnaTest
+          - LowGasSafeMathEchidnaTest
+          - UnsafeMathEchidnaTest
+          - FullMathEchidnaTest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up node
+        uses: actions/setup-node@v1
+        with:
+          node-version: 12
+
+      - name: Set up Python 3.8
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+
+      - name: Install node dependencies
+        run: yarn install --frozen-lockfile
+
+      - name: Install pip3
+        run: |
+          python -m pip install --upgrade pip
+
+      - name: Install slither
+        run: |
+          pip3 install slither-analyzer
+
+      - name: Install echidna
+        run: |
+          sudo wget -O /tmp/echidna-test.tar.gz https://github.com/crytic/echidna/releases/download/v1.6.0/echidna-test-v1.6.0-Ubuntu-18.04.tar.gz
+          sudo tar -xf /tmp/echidna-test.tar.gz -C /usr/bin
+          sudo chmod +x /usr/bin/echidna-test
+
+      - name: Run ${{ matrix.testName }}
+        run: echidna-test . --contract ${{ matrix.testName }} --config echidna.config.yml

contracts/test/BN256G2EchidnaTest.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.18;
+
+import "../BN256G2.sol";
+
+contract BN256G2EchidnaTest {
+    // Test the ECTwistAdd function
+    function checkECTwistAdd(
+        uint256 pt1xx, uint256 pt1xy,
+        uint256 pt1yx, uint256 pt1yy,
+        uint256 pt2xx, uint256 pt2xy,
+        uint256 pt2yx, uint256 pt2yy
+    ) public {
+        (uint256 sumXx, uint256 sumXy, uint256 sumYx, uint256 sumYy) = BN256G2.ECTwistAdd(
+            pt1xx, pt1xy, pt1yx, pt1yy,
+            pt2xx, pt2xy, pt2yx, pt2yy
+        );
+        assert(BN256G2.IsOnCurve(sumXx, sumXy, sumYx, sumYy));
+    }
+
+    // Test the ECTwistMul function
+    function checkECTwistMul(
+        uint256 s,
+        uint256 pt1xx, uint256 pt1xy,
+        uint256 pt1yx, uint256 pt1yy
+    ) public {
+        (uint256 mulXx, uint256 mulXy, uint256 mulYx, uint256 mulYy) = BN256G2.ECTwistMul(
+            s, pt1xx, pt1xy, pt1yx, pt1yy
+        );
+        assert(BN256G2.IsOnCurve(mulXx, mulXy, mulYx, mulYy));
+    }
+
+}
+

echidna.config.yml

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+#format can be "text" or "json" for different output (human or machine readable)
+format: 'text'
+#checkAsserts checks assertions
+checkAsserts: true
+#coverage controls coverage guided testing
+coverage: false
+# #psender is the sender for property transactions; by default intentionally
+# #the same as contract deployer
+# psender: "0x00a329c0648769a73afac7f9381e08fb43dbea70"
+# #prefix is the prefix for Boolean functions that are properties to be checked
+# prefix: "echidna_"
+# #propMaxGas defines gas cost at which a property fails
+# propMaxGas: 8000030
+# #testMaxGas is a gas limit; does not cause failure, but terminates sequence
+# testMaxGas: 8000030
+# #maxGasprice is the maximum gas price
+# maxGasprice: 100000000000
+# #testLimit is the number of test sequences to run
+# testLimit: 50000
+# #stopOnFail makes echidna terminate as soon as any property fails and has been shrunk
+# stopOnFail: false
+# #estimateGas makes echidna perform analysis of maximum gas costs for functions (experimental)
+# estimateGas: false
+# #seqLen defines how many transactions are in a test sequence
+# seqLen: 100
+# #shrinkLimit determines how much effort is spent shrinking failing sequences
+# shrinkLimit: 5000
+# #contractAddr is the address of the contract itself
+# contractAddr: "0x00a329c0648769a73afac7f9381e08fb43dbea72"
+# #deployer is address of the contract deployer (who often is privileged owner, etc.)
+# deployer: "0x00a329c0648769a73afac7f9381e08fb43dbea70"
+# #sender is set of addresses transactions may originate from
+# sender: ["0x10000", "0x20000", "0x00a329c0648769a73afac7f9381e08fb43dbea70"]
+# #balanceAddr is default balance for addresses
+# balanceAddr: 0xffffffff
+# #balanceContract overrides balanceAddr for the contract address
+# balanceContract: 0
+# #solcArgs allows special args to solc
+# solcArgs: ""
+# #solcLibs is solc libraries
+# solcLibs: []
+# #cryticArgs allows special args to crytic
+# cryticArgs: []
+# #quiet produces (much) less verbose output
+# quiet: false
+# #initialize the blockchain with some data
+# initialize: null
+# #whether ot not to use the multi-abi mode of testing
+# multi-abi: false
+# #benchmarkMode enables benchmark mode
+# benchmarkMode: false
+# #timeout controls test timeout settings
+# timeout: null
+# #seed not defined by default, is the random seed
+# #seed: 0
+# #dictFreq controls how often to use echidna's internal dictionary vs random
+# #values
+# dictFreq: 0.40
+# maxTimeDelay: 604800
+# #maximum time between generated txs; default is one week
+# maxBlockDelay: 60480
+# #maximum number of blocks elapsed between generated txs; default is expected increment in one week
+# # timeout:
+# #campaign timeout (in seconds)
+# # list of methods to filter
+# filterFunctions: []
+# # by default, blacklist methods in filterFunctions
+# filterBlacklist: true
+# #directory to save the corpus; by default is disabled
+# corpusDir: null
+# # constants for corpus mutations (for experimentation only)
+# mutConsts: [100, 1, 1]
+# # maximum value to send to payable functions
+# maxValue: 100000000000000000000 # 100 eth