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liza/test/dapi/AutoRetryTest.js

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/**
* Test case for AutoRetry
*
* Copyright (C) 2015 LoVullo Associates, Inc.
*
* This file is part of the Liza Data Collection Framework
*
* Liza is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
var dapi = require( '../../' ).dapi,
expect = require( 'chai' ).expect,
Class = require( 'easejs' ).Class,
DataApi = dapi.DataApi,
Sut = dapi.AutoRetry;
var _void = function() {},
_true = function() { return true; };
describe( 'dapi.AutoRetry trait', function()
{
/**
* If there are no retries, then AutoRetry has no observable effects.
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*/
describe( 'when the request does not need retrying', function()
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{
it( 'makes only one request', function( done )
{
var given = {};
// success (but note the number of retries presented)
var stub = _createStub( null, '' )
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.use( Sut( _void, 5 ) )
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();
stub.request( given, function()
{
expect( stub.given ).to.equal( given );
expect( stub.requests ).to.equal( 1 );
done();
} );
} );
/**
* We expect that any error will be proxied back to us; this is an
* important concept, since it allow separating the idea of a
* "retry" from that of a "failure": the latter represents a problem
* with the request, whereas the former indicates that a request
* should be performed once again.
*/
it( 'returns the response data, including any error', function( done )
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{
var chk = { foo: 'bar' },
chk_err = Error( 'foo' );
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var stub = _createStub( chk_err, chk )
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.use( Sut( _void, 1 ) )
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();
stub.request( '', function( err, data )
{
expect( err ).to.equal( chk_err );
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expect( data ).to.equal( chk );
done();
} );
} );
} );
/**
* This is when we care.
*/
describe( 'when the retry predicate is true', function()
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{
it( 'will re-perform request N-1 times until false', function( done )
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{
var n = 5;
var stub = _createStub( {}, {} )
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.use( Sut( _true, n ) )
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();
stub.request( {}, function( err, _ )
{
expect( stub.requests ).to.equal( n );
done();
} );
} );
it( 'will return most recent error and output data', function( done )
{
var e = Error( 'foo' ),
output = {};
// XXX: this does not test for most recent, because the return
// data are static for each request
var stub = _createStub( e, output )
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.use( Sut( _true, 1 ) )
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();
stub.request( {}, function( err, data )
{
expect( err ).to.equal( e );
expect( data ).to.equal( output );
done();
} );
} );
describe( 'given a negative number of tries', function()
{
it( 'will continue until a successful request', function( done )
{
var n = 10,
pred = function( _, __ )
{
return --n > 0;
};
var stub = _createStub()
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.use( Sut( pred, -1 ) )
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();
stub.request( {}, function( _, __ )
{
expect( n ).to.equal( 0 );
done();
} );
} );
} );
} );
describe( 'when the number of tries is zero', function()
{
it( 'will perform zero requests with null results', function( done )
{
var stub = _createStub( {}, {} )
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.use( Sut( _void, 0 ) )
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();
stub.request( {}, function( err, data )
{
expect( stub.requests ).to.equal( 0 );
expect( err ).to.equal( null );
expect( data ).to.equal( null );
done();
} );
} );
} );
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describe( 'when a delay function is provided', function()
{
it( 'will wait for continuation before retry', function( done )
{
var waited = false;
var wait = function( _, c )
{
waited = true;
c();
};
var stub = _createStub( {}, {} )
.use( Sut( _true, 2, wait ) )
();
stub.request( {}, function( _, __ )
{
expect( waited ).to.equal( true );
done();
} );
} );
it( 'will not process if continuation is not called', function()
{
var waited = false;
var wait = function( _, c )
{
waited = true;
/* do not invoke */
};
var stub = _createStub( {}, {} )
.use( Sut( _true, 2, wait ) )
();
// this works because we know that our stub is invoked
// synchronously
stub.request( {}, function( _, __ )
{
throw Error( "Should not have been called!" );
} );
expect( waited ).to.equal( true );
} );
it( 'will call delay function until predicate falsity', function()
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{
var n = 5;
var wait = function( tries_left, c )
{
n--;
// the first argument is the number of tries left
expect( tries_left ).to.equal( n );
c();
};
var pred = function()
{
return n > 0;
};
var stub = _createStub( {}, {} )
.use( Sut( pred, n, wait ) )
();
// this works because we know that our stub is invoked
// synchronously
stub.request( {}, _void );
// the first request counts as one, which brings us down to 4,
// but the wait function has not been called at this point; so,
// we expect that it will only be called four times
expect( n ).to.equal( 1 );
} );
it( 'allows aborting via failure continuation', function( done )
{
var err_expect = {},
out_expect = [];
var wait = function( _, __, abort )
{
abort();
};
// without aborting, this would never finish
var stub = _createStub( err_expect, out_expect )
.use( Sut( _true, -1, wait ) )
();
// this works because we know that our stub is invoked
// synchronously
stub.request( {}, function( err, output )
{
expect( err ).to.equal( err_expect );
expect( output ).to.equal( out_expect );
done();
} );
} );
} );
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} );
function _createStub( err, resp )
{
return Class.implement( DataApi ).extend(
{
given: null,
requests: 0,
'virtual public request': function( data, callback )
{
this.given = data;
this.requests++;
callback( err, resp );
}
} );
}