Create unit_testing.md

solidity/unit_testing.md

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+## Basic Unit testing
+
+A generic unit testing file looks like:
+
+
+```
+pragma solidity >=0.4.22 <0.8.0;
+import "remix_tests.sol"; // this import is automatically injected by Remix.
+import "remix_accounts.sol";
+// Import here the file to test.
+
+// File name has to end with '_test.sol', this file can contain more than one testSuite contracts
+contract testSuite {
+
+    /// 'beforeAll' runs before all other tests
+    /// More special functions are: 'beforeEach', 'beforeAll', 'afterEach' & 'afterAll'
+    function beforeAll() public {
+        // Here should instantiate tested contract
+        Assert.equal(uint(1), uint(1), "1 should be equal to 1");
+    }
+
+    function checkSuccess() public {
+        // Use 'Assert' to test the contract, 
+        // See documentation: https://remix-ide.readthedocs.io/en/latest/assert_library.html
+        Assert.equal(uint(2), uint(2), "2 should be equal to 2");
+        Assert.notEqual(uint(2), uint(3), "2 should not be equal to 3");
+    }
+
+    function checkSuccess2() public pure returns (bool) {
+        // Use the return value (true or false) to test the contract
+        return true;
+    }
+    
+    function checkFailure() public {
+        Assert.equal(uint(1), uint(2), "1 is not equal to 2");
+    }
+
+    /// Custom Transaction Context
+    /// See more: https://remix-ide.readthedocs.io/en/latest/unittesting.html#customization
+    /// #sender: account-1
+    /// #value: 100
+    function checkSenderAndValue() public payable {
+        // account index varies 0-9, value is in wei
+        Assert.equal(msg.sender, TestsAccounts.getAccount(1), "Invalid sender");
+        Assert.equal(msg.value, 100, "Invalid value");
+    }
+}
+```