HI, I am very new to VF and Apex Classes. 
I just created a VF page with a custom controller in Sandbox. Now I need to do unit test before deployment. I have no clue how to write the unit test:

What I built is a search page, user can type in search criteria and then click on search

Here is my Page:
<apex:page Controller="BannerAdsLocalController" id="page1">
  <!-- Begin Default Content REMOVE THIS -->
<h1>Search for Banner Ads Local</h1>
 
<apex:form id="searchForm"  >
<apex:outputLabel value="Category:" for="CategorySelected"/>

<apex:selectList id="Category" value="{!Category}" size="1" >
<apex:selectOptions value="{!Categories}"  />
</apex:selectList> 
&nbsp;&nbsp;&nbsp;

<apex:outputLabel value="Postcode:" for="postcode"/>
<input id="postcode" name="postcode" value="{!$CurrentPage.parameters.postcode}" size="15" maxlength="10" />
&nbsp;&nbsp;&nbsp;

<apex:outputLabel value="Start date:" for="startDate"/>
<input id="startDate" name="startDate" value="{!$CurrentPage.parameters.startDate}" size="7" maxlength="10" />(yyyy-mm-dd)
&nbsp;&nbsp;&nbsp;
<apex:outputLabel value="End date:" for="endDate"/>
<input id="endDate"   name="endDate"   value="{!$CurrentPage.parameters.endDate}" size="7"  maxlength="10" />(yyyy-mm-dd)
<input type="submit" name="search" value="Search" />
<br /><br />
</apex:form>

<apex:pageBlock title="Banner Ads Local Search Results"  rendered="{!NOT(ISNULL(Products))}"  >
<apex:pageBlockTable value="{!Products}" var="product">

<apex:column value="{!product.PricebookEntry.Name}"/>
<apex:column value="{!product.ListPrice}"/>

<apex:column headerValue="Opportunity Name" rendered="{!NOT(ISNULL(product))}" >
<apex:outputLink value="/{!product.Opportunity.id}">
{!product.Opportunity.Name}
</apex:outputLink>
</apex:column>
<apex:column value="{!product.Opportunity.StageName}"/>
<apex:column value="{!product.Opportunity.Campaign_Start_Date__c}"/>
<apex:column value="{!product.Opportunity.Campaign_End_Date__c}"/>


</apex:pageBlockTable>

</apex:pageBlock>

  <!-- End Default Content REMOVE THIS -->
</apex:page>

Here is my controller:
public class BannerAdsLocalController {

Transient List<OpportunityLineItem> Products;
Transient String Category  = null;
Transient String postcode  = null;
Transient Date   startDate = null;
Transient Date   endDate   = null;

Transient String s_start = null;
Transient String s_end   = null;

public List<SelectOption> getCategories()
{
    List<SelectOption> options = new List<SelectOption>();
   
    options.add(new SelectOption('','All categories'));

    Schema.DescribeFieldResult categoryField = Schema.sObjectType.Product2.fields.Categories__c;
    Schema.PicklistEntry [] values           = categoryField.getPickListValues();
   
    for(Schema.PicklistEntry val : values)
    {
      options.add(new SelectOption(val.getValue(), val.getLabel()));
    }
    return options;
}

public Date getStartDate()
{
    return startDate;
}

public Date getEndDate()
{
    return endDate;
}

public String getCategory()
{
    return Category;
}
public void setCategory(String Category) {
    this.Category = Category;
}


public List<OpportunityLineItem> getProducts()
{
  
   
    s_start  = ApexPages.currentPage().getParameters().get('startDate');
    s_end    = ApexPages.currentPage().getParameters().get('endDate');
    postcode = ApexPages.currentPage().getParameters().get('postcode');
   
    //dynamic SOQL, SOSL and dynamic DML are    currently in pilot, and not enabled for all organizations. If you need them
    //for your application and are interested in the pilot program, contact your salesforce.com representative.
    //so, we have to do the 6 combinnations:
    //Error: Compile Error: Dynamic Apex not allowed in this organization, so we have to do the following combinations:           
    //Products = Database.query(  conditions  + order_by );
   
    if (s_start != null && s_start<>'' && s_end != null && s_end <>'' && (Category=='' || Category == null) && (postcode ==null || postcode==''))
    {   
        //Date Range only:
        startDate = Date.valueOf(s_start);
        endDate   = Date.valueOf(s_end);

        Products = [SELECT  Opportunity.Id, Opportunity.Name,Opportunity.StageName,Opportunity.Payment_Stage__c,
                Opportunity.Amount,Opportunity.Campaign_Start_Date__c,  Opportunity.Campaign_End_Date__c,
                PricebookEntry.Name, PricebookEntry.ProductCode,PricebookEntry.Product2.Postcode__c,
                Quantity, TotalPrice, UnitPrice, ListPrice, Price_Ex_GST__c, Total_Ex_GST__c, ServiceDate,
                End_Date__c ,  Description 
                FROM OpportunityLineItem 
                WHERE     Opportunity.RecordTypeId= '012R00000008dGY'
                          AND 
                          (  
                            (Opportunity.Campaign_End_Date__c   >= :startDate and Opportunity.Campaign_End_Date__c   <= :endDate )    OR
                            (Opportunity.Campaign_Start_Date__c >= :startDate and Opportunity.Campaign_Start_Date__c <= :endDate )    OR
                            (Opportunity.Campaign_End_Date__c   >= :endDate   and Opportunity.Campaign_End_Date__c   <= :startDate )  OR
                            (Opportunity.Campaign_Start_Date__c >= :endDate   and Opportunity.Campaign_Start_Date__c <= :startDate )
                          )
               
                ORDER BY Opportunity.Campaign_End_Date__c,Opportunity.Name,ListPrice DESC 
                ];
    }
    else if ((s_start == null || s_start =='') && (s_end == null || s_end=='') && (Category !='' && Category != null) && (postcode == null || postcode == ''))
    {
        //only category selected:
   
        Products = [SELECT  Opportunity.Id, Opportunity.Name,Opportunity.StageName,Opportunity.Payment_Stage__c,
                Opportunity.Amount,Opportunity.Campaign_Start_Date__c,  Opportunity.Campaign_End_Date__c,
                PricebookEntry.Name, PricebookEntry.ProductCode,PricebookEntry.Product2.Postcode__c,
                Quantity, TotalPrice, UnitPrice, ListPrice, Price_Ex_GST__c, Total_Ex_GST__c, ServiceDate,
                End_Date__c ,  Description 
                FROM OpportunityLineItem 
                WHERE     Opportunity.RecordTypeId= '012R00000008dGY'
                          AND  PricebookEntry.Product2.Categories__c = :Category                          
                ORDER BY Opportunity.Campaign_End_Date__c,Opportunity.Name,ListPrice DESC 
                ];
    }
    else
    {
    ....
    }
    return Products;
}


}


Can someone give me some hints please?

Any feedback much appriciated!

Regards,

David